Climate of Sydney

The weather of the Sydney CBD is recorded at Observatory Hill.

Satellite imagery shows cloud cover obscuring the lights of the Sydney area at night, NASA, January 2011

Smoke haze in the Sydney Harbour during the Black Summer bushfires.

The climate of Sydney is humid subtropical (Köppen Cfa),^[1] shifting from mild and cool in winter to warm and hot in the summer, with no extreme seasonal differences as the weather is moderated by proximity to the ocean,^[2] although more contrasting temperatures are recorded in the inland western suburbs. Despite the fact that there is no distinct dry or wet season, rainfall peaks in the first few months of the year and is at its lowest just around the middle of the year, though precipitation can be erratic throughout the year.^[3][4][5] Precipitation varies across the region, with areas adjacent to the coast being the wettest.^[6] The city receives around 20 thunderstorms per year.^[7] According to the Bureau of Meteorology, Sydney falls in the temperate climate zone which has warm to hot summers^[a] and no dry season.^[8] Sydney's plant hardiness zone ranges from zone 11a to 9b throughout the metropolitan area.^[9]

Sydney has 109.5 clear days and 127.2 cloudy days annually,^[10] though it would have over 300 days of visible sunshine if one would count partly cloudy days or sunny breaks.^[11][12] Overall, Sydney has just about 66% of possible sun for Jun-Aug and around 54% for Dec-Feb, making winter sunnier than summer on average.^[13] Sydney's heat is predominantly dry in spring, but usually humid in the summertime,^[14] especially late summer – However, when temperatures soar over 35 °C (95 °F), the humidity is generally low as such high temperatures are brought by searing winds from the Australian desert.^[15][16] On some hot summer days, low pressure troughs increase humidity and southerly busters decrease temperatures by late afternoon or early evening.^[17][18] In late autumn and winter, east coast lows can bring large amounts of rainfall.^[19] When the subtropical ridge is north of Sydney in late winter to early spring, the wind would come from the west or inland. As the ridge moves south in summer and autumn, the winds become easterly.^[20][21][22]

Sydney experiences an urban heat island effect,^[23] making certain parts of the city more vulnerable to extreme heat, particularly the west.^[23] Efforts have been introduced to investigate and mitigate this heat effect, including increasing shade from tree canopies, adding rooftop gardens to high rise structures and changing pavement colour.^[24][25] The El Niño Southern Oscillation, the Indian Ocean Dipole and the Southern Annular Mode^[26][27] play an important role in determining Sydney's weather patterns: drought and bushfire on the one hand, and storms and flooding on the other. Sydney is prone to heat waves and drought, which have become more common in the 21st century.^{[28][29][30][31]}

Seasons[]

Summer[]

Beaches are a common visit among residents and tourists alike in a Sydney summer (Bondi Beach).

Storm clouds over Coogee Beach. Sydney summers are characterised by rapid changes of weather, with humidity and rain not uncommon to the city although thunderstorms are more common in the west..

Summer in Sydney tends to vary, but it is generally warm to hot.^[32] Though at times, sea breezes would moderate the temperatures and raise humidity. Temperatures tend to be stable in late summer where they rarely go below 21 °C (70 °F) or over 40 °C (104 °F), unlike late spring and early summer where such extremes would occur.^[10]

When temperatures reach over 30 °C (86 °F), the relative humidity seldom exceeds 45%, although low pressure troughs can increase humidity in some hot days, especially in late summer, where they may provide afternoon thunderstorms that are usually accompanied by heavy rainfall and, at times, hail. Furthermore, most mornings and nights would be muggy, with the 9am relative humidity ranging from 69% to 75%.^[10][33] The average 3pm dewpoint temperature in the summer ranges from 16.2 °C (61.2 °F) at the coast, to 14.4 °C (57.9 °F) inland. Dewpoints would be higher in late summer, reaching 20 °C (68 °F), especially in the mornings and evenings, although they would usually be lower in the heat of the day, dipping as low as 9 °C (48 °F) in the extremely hot day.^[34]

In late spring and summer, Sydney can sometimes get northwesterly winds from the Outback, which are dry and hot, making the temperatures soar above 38 °C (100 °F), with the relative humidity as low as 15%. This happens after the northwesterlies are carried entirely over the continental landmass, not picking up additional moisture from a body of water and retaining most of their heat. On these occasions, Sydney can experience the fury of the desert climate,^[35] although they are often ended with a Southerly Buster, which is a windy, shallow cold front that sweeps up from the southeast abruptly cooling the temperature. At times, it may be accompanied by a thunderstorm and drizzle, and it may keep the temperatures cool the following few days as well.^[36][37]

In the Sydney central business district, an average of 15 days a year have temperatures of more than 30 °C (86 °F) and 3 days with temperatures over 35 °C (95 °F).^[10] In contrast, western suburbs such as Liverpool and Penrith have 41 and 67 days with temperatures above 30 °C (86 °F), 10 and 19 days above 35 °C (95 °F), and, 1 and 4 days above 40 °C (104 °F), respectively.^[33][38]

The highest recorded maximum temperature at Observatory Hill was 45.8 °C (114.4 °F) on 18 January 2013 during a prolonged heat wave across Australia from early December 2012 to late January 2013.^[39] The highest recorded minimum at Observatory Hill is 27.6 °C (81.7 °F), registered on 6 February 2011.^[10] A similar minimum temperature has also been recorded in the western suburbs.^[33] The highest recorded maximum temperature for the western suburbs was recorded at Penrith with a high of 48.9 °C (120 °F) on 4 January 2020.^[40]

Autumn[]

Autumn leaves observed in Centennial Park, Sydney.

Late summer conditions usually continue until the first few weeks of April where maximum temperatures hover around 25 °C (77 °F) and 29 °C (84 °F) with the dewpoint being around 16 °C (61 °F) and 17 °C (63 °F) on average. Although, unlike late summer, the nights may be seemingly cooler and crispier. Most heavy rainfall events usually occur in late summer and early autumn as the subtropical ridge of high pressure, which rotates counterclockwise, is to the south of Australia and would therefore give way for moist easterlies from the Tasman Sea and as well as low pressure systems to penetrate the region.^[26][22]

The transition from late summer to autumn is gradual, where noticeably cooler and crisper conditions taking in effect by around mid-April. In mid-autumn, the highs typically average at a pleasant 22 °C (72 °F) or 23 °C (73 °F), rarely going above 30 °C (86 °F) or below 20 °C (68 °F). In May, the average highs would be around 20 °C (68 °F) and 19 °C (66 °F) with cool and usually humid nights, that seldom dip below 10 °C (50 °F). Wintry highs of 18 °C (64 °F) may be expected in the last week of autumn.^[41]

Temperatures in autumn are usually consistent and stable, lacking any extremes that tend to be experienced in spring and summer. Due to moist easterlies that prevail in this season, foggy mornings and overcast conditions should be expected. The average 9am relative humidity in autumn ranges from 72% to 80% in the Sydney region, the highest in the year.^[33] The lowest maximum temperature in autumn is 11.3 °C (52.3 °F), recorded on 24 May 1904.^[10]

Winter[]

In winter, the diurnal range in the western suburbs is relatively high, with temperatures being as high as 19 °C (66 °F) during the day and as low as 3 °C (37 °F) at night. Such low temperatures may provide mild to moderate frost in the western suburbs.^[42] Winter in central Sydney tends to be more mild where the lows rarely drop below 5 °C (41 °F), and highs hovering at around 16 °C (61 °F) and 17 °C (63 °F) mainly due to proximity to the ocean.^[10] Furthermore, it is worth noting that Sydney CBD (Observatory Hill) has never recorded frost, whereas coastal cities in the country on similar latitudes, such as Perth, Esperance and Adelaide, and those further north of Sydney such as Coffs Harbour, Port Macquarie, Hervey Bay and Sunshine Coast, have recorded frost or temperatures below 0 °C (32 °F).^[10]

A foggy winter morning in the Sydney Harbour.

In the west, Liverpool and Richmond have 4 and 38 nights, respectively, where temperatures dip below 2 °C (36 °F). On average, only 1 night in Liverpool and 17 nights in Richmond have lows going below 0 °C (32 °F). The lowest maximum temperature in Liverpool was 8.2 °C (47 °F), recorded on 28 July 1981. Similar low maximums have been recorded in the Sydney region in winter.^[33] 9am humidity ranges from 61% to 74% across the Sydney region, with the more higher figures experienced in June mornings. Highs of 12 °C (54 °F), whilst rare, are not unheard of in winter.^[10][33]

Sydney receives around 15 days of fog annually,^[43] which occurs in winter mornings, but more often in June when moist easterlies dominate. The inland suburbs would generally receive radiation fog thanks to nocturnal cooling under a clear sky of humid maritime air that was brought inland by the previous day's sea breeze. The coastal suburbs would mostly get an advective fog, which floats ashore from the meeting of warm water offshore and cold water nearby on the land. Heavier rain and cloudiness are also to be expected more in June, on average, than the latter winter months.^[44]

During late winter, warm dry westerly winds which dominate may raise the maximum temperatures as high as 27 °C (81 °F) in some instances. As the subtropical ridge is north of Sydney in mid-late winter, it picks up dry westerlies from the continent's interior because of its anticlockwise rotation, thus producing more sunny days in the region,^[26] hence why August has the highest sunshine percentage than any other month.^[45]

The lowest recorded minimum at Observatory Hill was 2.1 °C (35.8 °F) on 22 June 1932,^[10] while the coldest in the Sydney metropolitan area was −8 °C (18 °F), in Richmond. The lowest recorded maximum temperature at Observatory Hill was 7.7 °C (45.9 °F). Although not usually considered a suburb of Sydney, Picton, a town in the Macarthur Region of Sydney, recorded a low of −10.0 °C (14.0 °F) on 16 July 1970.^[46]

Spring[]

Jacaranda trees bloom ostentatiously in springtime, where they attract sightseers and photographers.^[47]

Early spring is rapidly transitional. Cool conditions from late winter may continue in September with the maximum temperature dipping as low as 18 °C (64 °F) at the coldest, but due to the drastic transition, temperatures above 30 °C (86 °F) can also be expected in that month. By November, summery conditions begin, with temperatures normally ranging between 24 °C (75 °F) and as high as 30 °C (86 °F), albeit with relatively low humidity.^[48]

Because the subtropical ridge lies to the north of Sydney this time of the year, it will bring westerly winds from the interior that produce mostly sunny conditions,^[26][22] at times warm, with the temperatures averaging between 21 °C (70 °F) and 25 °C (77 °F) with relatively low dewpoints, hovering between 4 °C (39 °F) and 12 °C (54 °F). Some days may be windy due to the dry westerlies and nights may be relatively cool, where temperatures plummet down to around 7 °C (45 °F) in some suburbs. Hot air from the interior that soar temperatures to over 35 °C (95 °F) can be expected, especially in the months of October and November. These conditions are rare in September, but not unheard of.^[42]

Extreme, changeable and inconsistent temperatures are much more prevalent in spring than other seasons. In some occasions, hot dry days are cooled down by a southerly buster, which eventually lower the temperatures from 40 °C (104 °F) to as low as 19 °C (66 °F).^[49] Such extremes usually happen in mid-late spring. Other seasons seldom see such fluctuations in a day's span. Furthermore, the diurnal range is higher in this season than it is in autumn.^[10]

The lowest maximum temperature in spring was 9.5 °C (49.1 °F), recorded on 8 September 1869.^[10] 9am relative humidity is the lowest in the year during spring, ranging from 58% to 68%, with early spring receiving lower figures.^[33]

Microclimate[]

Streets with tree canopy, which are usually found in the inner-west and northern Sydney, tend to have lower air temperatures (Summer Hill).^[50]

Streets without tree cover, usually found in recent suburbs in the west, would experience hotter temperatures due to heat radiation (Plumpton).^[51]

The region of Sydney is subject to phenomena typical of a microclimate, namely in late spring and summer, where the western suburbs would be hotter than the Sydney CBD by 6–10 °C (11–18 °F)^[52] due to urban sprawl exacerbating the urban heat island effect and less exposure to mitigating sea breezes which cool down Sydney's eastern edge and would fail to move 9 km (5.6 mi) inland. The dramatic temperature difference between coastal and inland areas is caused by a combination of desert-warmed air from central Australia reaching the west, and as well as density of housing, lack of vegetation or open spaces, and the Blue Mountains which help trap the hot air.^[53][54]

When it is 25 °C (77 °F) at Bondi for instance, the temperature will be around 30 °C (86 °F) just west of the Sydney Harbour Bridge, around 35 °C (95 °F) near Parramatta and as much as 40 °C (104 °F) 40 km (25 mi) inland. Such extreme temperature differences in the Sydney metropolitan area usually occur in late spring when the western Pacific Ocean is still quite cool and the inland air is warm.^[55] Furthermore, within the CBD, heat maps show the area around Central Station (in Haymarket) is 0.5–1.0 °C (1–2 °F) warmer than Circular Quay and surrounds, making it the hottest place in the CBD.^[56]

According to ecologist, Dr Sebastian Pfautsch from the University of Freiburg, in Sydney's hot days there could be discrepancies of up to 22 more days above 40 °C (104 °F) recorded in urban space compared to a weather station from the Bureau of Meteorology.^[57] Because 48.9 °C (120.0 °F) was recorded in Penrith (on 4 January 2020), it won't be unusual to have a 50 °C (122 °F) reading somewhere nearby, especially if it lacked green space and retained heat to intensify heatwave temperatures.^[53] Moreover, a heat logger registered a temperature of 52.0 °C (125.6 °F) at Berkshire Park, making it the hottest temperature ever recorded in the Sydney basin, albeit being an unofficial one.^[58][59] Richmond has the second largest overall temperature range recorded in Australia, after Mitchell, Queensland; −8.3 °C (17.1 °F) to 47.8 °C (118.0 °F).^[60][61]

Urban heat island[]

Waterbodies and open spaces provide cooling benefits in urban areas (Parramatta River, Parramatta).^[54]

A study by the University of Western Australia and RMIT indicated that the western suburbs have a much stronger urban heat island effect than those east of the CBD and that hotter temperatures in the west are human contributed due to solar radiation absorbing materials in black asphalt and dark roofs, anthropogenic heat from cars and less natural environments, thereby creating a "heat dome" that blocks the cooler air from the sea. Greening Australia stated that January mean maximum temperatures in the west have risen at a pace of 0.65 °C per decade, over twice as much as eastern Sydney's 0.28 °C per decade.^[62] The OEH warned that further development could cause more exceedingly hot days in the west by 2030.^[54] Annually, coastal Sydney sees five heat-related deaths per 100,000 people while the western suburbs see 14 per 100,000.^[56]

Urban heat island of the CBD has been efficaciously blocking the cooler air from reaching the inland suburbs because the CBD's "high temperature, is like a wall that stops the sea breeze in its tracks. Over Sydney’s CBD is a heat dome because of the high density of concrete and asphalt. If we want to cool western Sydney and demolish this wall, we need to cool the CBD first", Professor Mattheos Santamouris from UNSW states. He explained that cooling the CBD would reduce the temperature by 1.5 °C in the west and tree coverage could cool down suburban streets by as much as 10 °C (50 °F) in hot days since high-density housing developments and scarce trees trap heat.^[56][63][51]

According to climate researchers, relatively easy modifications such as constructing fountains and water playgrounds could also lower temperatures in the western suburbs. The city now has 3.6% more trees in 2016 than it did in 2009 and Penrith City Council had planned to plant 100,000 trees from August 2018, in addition to planning a large city park, creating a water-sensitive urban design, street shading, and the use of cool materials in its building developments.^[64] Furthermore, Parramatta City Council has installed 20 temperature sensors among different tree species in its suburbs to compare how different species can help reduce urban heat.^[65][66]

Plant hardiness zone[]

Royal Botanic Gardens, lying in the highest hardiness zone at 11a, with palm trees and subtropical vegetation.

The Hawkesbury valley, covered in frost, has the lowest hardiness zone in Sydney at 9b.

Due to the microclimate, the plant hardiness zone in the Sydney area would range:^[9]

• Zone 11a (4.4 to 7.2°C):
  • Sydney CBD
  • Sydney Harbour
  • North Sydney
  • Lower North Shore, which includes Mosman Bay and Chatswood
• Zone 10b (1.7°C to 4.4°C):
  • Northern Beaches
  • Inner west
  • City of Parramatta
  • Eastern portion of Canterbury-Bankstown and Cumberland City Council (or eastwards from Lidcombe and Lakemba)
  • North Shore
  • Eastern suburbs
  • Georges River Council
  • Southern Sydney
• Zone 10a (-1.1°C to 1.7°C):
  • Most of Cumberland Plain, which include the cities of Fairfield, Blacktown, Penrith, Liverpool and Campbelltown
  • Hornsby Shire
  • Hills District
• Zone 9b (-3.9°C to -1.1°C):
  • City of Hawkesbury, which includes Richmond and Windsor

Warm and cool periods[]

York Street during the 2009 Australian dust storm.

The Bureau of Meteorology reported in 2011 that 2002 to 2005 had been the warmest years in Sydney since records began in 1859. 2004 saw an average daily maximum temperature of 23.4 °C (74.1 °F), 2005 of 23.4 °C (74.1 °F), 2002 of 22.9 °C (73.2 °F), and 2003 of 22.7 °C (72.9 °F). The average daily maximum between 1859 and 2004 was 21.6 °C (70.9 °F). Seven (of the ten) warmest years in 151 years of recordkeeping have occurred in the ten years between 2001 and 2010, with this decade being the warmest on record for minimum temperatures.^[67][68]

The Bureau of Meteorology reported that the summer of 2007–08 was the coolest in 11 years, the wettest in six years, the cloudiest in 16 years, and one of only three summers in recorded history to lack a maximum temperature above 31 °C (88 °F).^[69] The Bureau of Meteorology reported that 2009 was a warm year. The average annual daytime temperature at Observatory Hill was 22.9 °C (73.2 °F), which is 0.9 °C (1.6 °F) above the historical annual average. This ranks as the seventh highest annual average maximum temperature since records commenced in 1859.^[70] 2010 was the equal fourth warmest year on record for Sydney, with an average maximum of 22.6 °C (72.7 °F), which was 0.6 °C (1.1 °F) above the historical annual average.

In 2013, the city had the warmest July and September on record,^[71][72] with September being one of the driest. In September, temperatures were 4 °C (7 °F) above average^[73] and the city had over seven days where temperatures reached 28 °C (82 °F), making it more similar to November's weather pattern.^[74] October 2015 had the warmest nights on record, which were 3.3 °C (5.9 °F) above average.^[75] The warming trend continued in 2016 as Sydney's warmest autumn ever was recorded.^[76] July 2017 to June 2018 in southeastern Australia proved to be the hottest financial year on record with maximum temperatures being the warmest on record and minimums above average.^[77]

Sydney experienced its hottest summer since records began in the summer of 2016–17, with more than 10 days over 35 °C (95 °F). Sydney's 2017 mean temperature of 19.5 °C (67.1 °F) degrees was 1.7 °C (3.1 °F) degrees above the long term average and the second highest value in 158 years of records. The warmest year on record was 2016, with a mean temperature of 19.6 °C (67.3 °F) degrees.^[78] On 7 January 2018, Sydney was the hottest place on Earth.^[79] In April 2018, Sydney had the longest running hot spell for that month with nine consecutive days of temperatures reaching 25 °C (77 °F). Furthermore, the airport and parts of the western suburbs also broke heat records in that month.^[80]

The 2020-21 summer was the coolest in a decade due to La Nina's influence.^[81] During May 2021, Sydney CBD recorded its coldest stretch of May days in 54 years due to a polar blast that swept across Australia's southeast, which kept the temperatures below 9 °C (48 °F) in the early mornings for five consecutive nights, in addition to the inland suburbs dipping down to 1 °C (34 °F) and 5 °C (41 °F).^[82] On June 10 2021, Sydney CBD had its coldest day since 1984 and the coldest June day since 1899, where it reached a maximum of just 10.3 °C (50.5 °F). Bankstown, a western suburb, only reached 9.7 °C (49.5 °F), its coldest day in 50 years, with nearby suburbs registering a similar temperature.^[83] These unusually cold maximums were caused by a cut-off low, which is a slow moving, sizeable Antarctic cold air mass that got "cut-off" from the westerly trough systems of cold air in the south where it reached the east coast.^[84] August 2021 registered 15 consecutive winter days above 20 °C (68 °F), the first time in 163 years of records, which was achieved due to a lack of cold fronts or rain over NSW during the month and a blocking high in Southern Australia that prevented cold fronts from reaching the continent.^[85]

Precipitation[]

Rainfall seasonality[]

A thunderstorm cloud over Bondi in March 2016.

Rainfall is slightly higher or dominant during the first half of the year, particularly in late summer and early autumn,^[86] when the subtropical ridge is to the south of the continent, thereby allowing easterly winds and low pressure systems to dominate on the east coast. Rainfall will tend to be lower in the second half of the year when the subtropical ridge is to just the north of the city where it picks up dry winds from the continent's interior towards Sydney (as it rotates counter-clockwise) and this will be when clockwise-rotating low pressure systems are to the south of the continent.^[22][87][88]

Due to the unpredictability of rain, the wettest and driest months would change on a yearly basis. The "wet" and "dry season" is more pronounced in the inland suburbs with late winter to early spring (August–September) having a drying trend and late summer to early autumn being wetter and greener (February–March).^[89] The drier winters are owed to its rain shadow position on the leeward (eastern) side of the Great Dividing Range, which shield the region from south-westerly cold fronts that arrive from the Southern Ocean.^[90][91] Though east coast lows, which are an intense cut-off low system that strike from the southeast in the Tasman Sea, would provide heavy rainfall typically in late autumn and early winter. Other rainfall drivers include Black nor'easters (in the warm months), Tasman lows (between autumn and spring), Australian northwest cloudbands (all year round) and as well as, albeit rarely, tropical cyclone remnants.

The annual evaporation rate for Sydney is 1,600 mm (62.99 in),^[92] with the rate in the summer being 600 mm (23.62 in)^[93] and in winter 300 mm (11.81 in).^[94]

Rainfall amount[]

Within the city and surrounds, rainfall varies, from around 700 mm (27.56 in) at Badgerys Creek^[95] (in the west) to 1,400 mm (55.12 in) at Turramurra (the northeast) in the Northern Suburbs, which create an orographic rainfall.^[96] Even in its months of highest rainfall, Sydney has relatively few rainy days, with an average mean of 7 to 8 rainy days per month on the 1 mm (0.04 in) threshold, despite having a moderate to high amount of annual rainfall at around 800 mm (31.50 in) to 1,100 mm (43.31 in) (depending on the area) – This illustrates that Sydney generally receives short-lived, heavy rainfall day events, usually not lasting more than 2 or 3 days, which give away to mostly propitious conditions for many weeks to months even, especially during an El Niño period (though during a La Niña event, rainfall may be intermittent for many days or weeks).^[97]

Rain hours are longer in the winter than in the summer, with rainfall lingering on for the whole day. In some days, rain may come in drizzle form, though this is rare as most rain comes mostly from major storms. In the warm months, rain comes in short heavy downpours in the afternoons, usually cooling the conditions and providing some respite.^[98] Sometimes these afternoon showers give away to the sun again, although black nor'easters may provide rainfall for a few consecutive days.^[99][10][33]

Storms[]

Heavy hailstorm in Pagewood, April 2015.

Sydney experiences east coast lows, which tend strike between the months of May and August (though they can occur in other months as well), usually during a positive SAM phase.^[100] The precipitation of the low comes from a nimbostratus cloud that would dump as much as 70 mm (2.76 in) of rain for as much as two days, though when the cloud is thick enough 100mm of rain can fall in three hours as was the case in August 1986.^[101] Also in winter, thanks to onshore winds and Sydney's coastal proximity, the CBD would be susceptible to some light rain and drizzle – These conditions usually don't penetrate the inland suburbs. However, the western suburbs experience thunderstorms more often then the CBD and eastern suburbs due to a capping inversion and flat topography although thunderstorms do occasionally occur in the eastern suburbs expressly when there is a north east seabreeze as was the case during the 1947 event.

The city is rarely affected by cyclones, although remnants of ex-cyclones do affect the city.^[102] The city is prone to severe hail storms, such as the 1947 Sydney hailstorm, wind storms, and flash flooding from rain caused either by East Coast Lows (such as the major storm in early June 2007) or ex-tropical cyclone remnants. East Coast Lows are low pressure depressions that can bring significant damage by heavy rain, cyclonic winds and huge swells. Scientists have predicted that rainfall will become more unpredictable and temperatures will be on the rise.^[103][104] Parts of western Sydney were substantially flooded during the New South Wales 2021 floods, with many areas around Richmond and Windsor submerged in floodwaters.^[105]

Snowfall[]

June 1836[]

Snow is extremely rare in Sydney and was last reported in the Sydney area in 1836 where thousands of convicts and the British settlers in Hyde Park woke up to snow "nearly an inch deep" on June 28. The meteorological table in The Sydney Herald recorded that on the morning of the snow the temperature dropped to 3 °C (37 °F). A keeper of weather observations during that period, T. A. Browne noted:^[106]

The years 1836, 1837 and 1838 were years of drought, and in one of these years (1836) a remarkable thing happened. There was a fall of snow; we made snowballs at Enmore and enjoyed the usual schoolboy amusements therewith.

The Sydney Morning Herald reported on the event, saying:

For the first time in the memory of the oldest inhabitants, snow fell in Sydney on the morning of Tuesday last. 27 June 1836, about 7 o'clock in the morning, a drifting fall covered the streets nearly one inch in depth...A razor-keen wind from the west blew pretty strongly at the time and altogether, it was the most English like winter morning ever experienced.

The Sydney Monitor reported:^[107]

We believe snow was never seen in Sydney before the previous night. The weather was cold, but not more so than we have often felt it before.

July 2008[]

On 27 July 2008, a fall of graupel, or soft hail, blanketed Lindfield, Roseville and Killara in white, as it was cold enough to prevent the soft hail from melting when it fell, thereby preserving it as a soft, melting ice when it reached the ground. Because of its snow-like appearance, the graupel was mistaken by many residents for snow.

Owing to this event, a senior forecaster from the Bureau of Meteorology doubted the 1836 snow account, stating weather observers in that time period lacked the technology and skill to distinguish snow from soft hail.^[108]

Blue Mountains[]

The Blue Mountains, a temperate oceanic region bordering on Sydney's metropolitan area, have a reputation for snow in winter, with places such as Katoomba, Leura and Blackheath receiving the most snow due to their higher elevation. Despite the reputation, there are only around five snowy days per year in the upper mountains area with two settled falls per season, and another five to ten days of light snow showers or sleet. Settled snow has become less common in recent decades.^[109] It is extremely rare to see snow below Lawson.^[110]

Wind[]

Averaging at 13.8 km/h (8.6 mph), November is the windiest month, whilst March is the calmest at 11.3 km/h (7.0 mph) in the CBD.^[10] Some suburbs in the metropolitan area tend to be the windiest in January, September, October or December, and calmest in the months of May or June.^[111][112] As a whole, the Sydney region is generally the windiest from October to January and calmest from March to June. The more windier locations are those by the coast, such as the eastern suburbs. The prevailing wind annually is northeasterly. In the warm months, only 40% of the time Sydney would get wind directions from the northwest or southwest, which are the dry winds flown from the heated interior of Australia.^[113]

Northeasterlies and easterly sea breezes are dominant from early summer to early autumn, because the anticlockwise-rotating subtropical ridge is to the south of the city where it allows winds from the sea to penetrate. Westerlies are dominant in late winter to mid-spring as the subtropical ridge is just to the north of the city, picking up winds from the interior and blocking easterlies from the sea.^[22]

Southerly busters are expected from October to the end of March. They typically look like as if a sheet of cloud is rolled up like a scroll by the advancing wind. The change of wind (in the warm months) is sometimes very sudden, where it may be fresh northeasterly and in ten minutes a southerly gale. Katabatic winds are light, south-westerly drainage winds, akin to land breezes, that occur when air of higher density in the Blue Mountains descends under gravity force into the Sydney metropolitan area and the Hawkesbury Basin, usually during a winter night.^{[114][115][116]}

Föhn effect[]

Föhn wind illustration (Left: Great Dividing Range, Right: Sydney).

Since Sydney straddles the Great Dividing Range's eastern side, and thus falls on its rain shadow, it would experience a Föhn-like type of wind,^[117] which is a dry south-westerly that raises the air temperature in the lee of the mountains and reduce atmospheric moisture due to the partial orographic obstruction of comparatively damp low-level air and the subsiding of drier upper-level air in leeward of the mountains. As the moist air rises, it cools and it would condense, thereby creating precipitation on the upwind slopes. The precipitation then gets rid of the moisture from the air mass on the lee side, and the condensation raises the air temperature as it descends the lee slopes because of the adiabatic compression.^[118]

During this condition, an orographic cloud band, or the Föhn wall, builds up along the ridgelines of the NSW highlands due to condensation of moisture as the air ascends the windward slopes. Meanwhile, the Föhn arch, with its broad layer of altostratus cloud, shapes downwind of the mountains in the ascending component of a standing lee mountain wave. In weather maps, a band of clear air called the Föhn gap, which is over the downwind of the Blue Mountains region, can be seen between the wall and arched cloud cover. Much like the Santa Ana winds in California, they may elevate fire danger in the warmer months, due to their dry, gusty nature.^[119][120]

In the cool season, Föhn-like winds can be particularly damaging to homes and would affect flights, in addition to being uncomfortable, as the wind chill factor would usually make the temperatures feel cooler than what they are.^[121] These south-westerly winds, which average between 60 km/h (37 mph) to 70 km/h (43 mph), are generally brought on by a large polar air mass or a deep low pressure system from the southwest of the continent in the Southern Ocean which advances northwards across Victoria towards the east coast.^[122][123] Typically occurring from winter to spring, though more common between July and September (when westerly cold fronts become more frequent), the winds would usually cause rainfall, snowfall and/or sleet in the windward side of the mountains, but would provide clear and relatively warmer conditions on the leeward side of the mountain range in the Sydney region and much of the southeast coastal plains.^[124]

Drought[]

Smoke from the 2013 New South Wales bushfires.

Sydney's climate appears to be becoming drier; The city has had fewer rain days in recent years than shown in the long-term climate table above. In summer, Sydney can go for long periods without rainfall. The other phenomenon that arises from these long, dry and hot periods is bushfires, which occur frequently in the areas surrounding the city. Water supply is a recurring concern for the city during drought periods. In 2005 the reservoirs reached an all-time low. However, water levels since then have recovered in 2013.

Many areas of the city bordering bushland have experienced bushfires, notably in 1994 and 2001–02 — these tend to occur during the spring and summer. Heatwaves, which are regularly occurring in recent years, would usually lead to water restrictions and a high risk of bushfires, which sometimes bring a smoky haze to the city. Smog is noticeable on hot days, even without bushfires.^{[125][126][127]}

The years 2009 and 2010 had dry conditions, according to Bureau of Meteorology.^[128] On 23 September 2009, a dust storm that started in South Australia and inland New South Wales blanketed the city with reddish orange skies early in the morning. Originating from the north-eastern region of South Australia, the dust storm lifted thousands of tons of dirt and soil which were then dumped in Sydney Harbour and the Tasman Sea.^[129] It stretched as far north as southern Queensland and it was the worst dust storm in 70 years.^[130] During that year, Sydney experienced a number of warm winter days, dry gusty winds and another milder dust storm.^[131][132]

The November 2018 dust storm over Port Jackson as seen aloft.

In 2011, Sydney had the driest February in 30 years with only 18 mm (0.71 in) of rain falling, which is well below the average of 118 mm (4.6 in). Some of the western suburbs recorded the lowest total February rainfall on record.^[133] In September 2013, the combination of dry weather, warm temperatures and strong winds brought early-season bushfires. Major bushfires impacted western Sydney and the Blue Mountains, resulting in some evacuations, closed roads, and destroyed homes.^[72] The summer of 2013-14 was the driest in 72 years. The precipitation of December 2013 and January 2014, inclusively, only added up to 48.4 mm (1.91 in), which is only a quarter of a typical amount for December and January. Observatory Hill only received 17 mm (0.67 in) of rain in January.^[134]

September 2017 was the driest on record, with the gauge receiving only 0.2 mm (0.0079 in) of rain. Furthermore, in that year, the city received less than half of its long-term average rainfall between July and December.^[135] In the late morning and early lunchtime of 22 November 2018, a dust storm, stretching about 500 kilometres, swept through Sydney due to a low pressure trough and cold front that picked up dry soil in drought-ridden areas of far western NSW that week. Milder compared to the 2009 storm, the effect of the dust was still apparent across iconic locations such as the Sydney Opera House and Sydney Harbour Bridge.^[136]

Furthermore, 2018 in Sydney has been one of the driest in a century, with the Greater Western Sydney farming region being the worst affected.^[137] Due to the widespread bushfires in December 2019, which even affected the western periphery of the city, the Sydney metropolitan area suffered from dangerous smoky haze for several days throughout the month, with the air quality being 11 times the hazardous level in some days,^[138][139] even making it worse than New Delhi's,^[140] where it was also equalled to "smoking 32 cigarettes."^[141] 2019 was one of Sydney's warmest in 161 years and the driest since 2005, which had a few days of raised dust and as well as declining dam levels. Rainfall in December was just 1.6 millimetres at Observatory Hill, overthrowing the record low of 2.8 millimetres recorded for the month in 1979.^[142]

Historical season descriptions[]

Aboriginal[]

The Sydney Basin was in the Tharawal country. Each clan had knowledge of their area and the season changes. These were the seasons of the Sydney region according to the Aboriginal people living there:^[143]

• January–March (Burran): Hot and dry
• April–June (Marrai'gang): Wet, becoming cooler
• June–July (Burrugin): Cold, frosty, short days
• July–August (Wiritjiribin): Cold and windy
• September–October (Ngoonungi): Cool, getting warmer
• November–December (Parra'dowee): Warm and wet

British[]

In 1819, British explorer William Wentworth described Sydney's climate as:^[144]

Highly salubrious and delightful, although the heats in summer are sometimes excessive, the thermometer frequently rising in the shade to 90 °F (32 °C), and even to a 100 °F (38 °C) and upwards of Fahrenheit – This, it must be admitted, is a degree of heat that would be highly oppressive to Europeans, were it not that the sea breeze sets in regularly about nine o'clock in the morning. If the summers are occasionally a little too hot for the European constitution, it will be remembered that the extreme heats which I have noticed as happening during the north-west winds, are of but short continuance; and that the sea and land breezes, which prevail at this season in an almost uninterrupted succession, moderate the temperature so effectually, that even new comers are but little incommoded by it. The hot season, however, which is undoubtedly the most unhealthy part of the year, does not, as will have been perceived, continue above four months. The remaining eight possess a temperature so highly moderate and congenial to the human constitution, that the climate of this colony would upon the whole, appear to justify the glowing enthusiasm of those who have ventured to call it the Montpellier of the world.

Below, Wentworth describes Sydney's^[b] seasonal and annual weather patterns in analytical detail:^[144]

A rainy day in Redfern (Arthur Streeton, 1893)

Summer

During these three months violent storms of thunder and lightning are very frequent, and the heavy falls of rain which take place on these occasions, tend considerably to refresh the country, of which the verdure in all but low moist situations entirely disappears. At this season the most unpleasant part of the day is the interval which elapses between the cessation of the land breeze and the setting in of the sea. This happens generally between six and eight o'clock in the morning, when the thermometer is upon an average at about 72 °F (22 °C). During this interval the sea is as smooth as glass, and not a zephyr is found to disport even among the topmost boughs of the loftiest trees.

Autumn

The weather in March is generally very unsettled. This month, in fact, may be considered the rainy season, and has been more fertile in floods than any other of the year. The thermometer varies during the day about 12 °C, being at day-light as low as from 55 to 60 °F (13 to 16 °C), and at noon as high as from 70 to 75 °F (21 to 24 °C). The sea and land breezes at this time become very feeble, although they occasionally prevail during the whole year. The usual winds from the end of March to the beginning of September, are from S. to S. W.

The weather in the commencement of April is frequently showery, but towards the middle it gradually becomes more settled, and towards the conclusion perfectly clear and serene. The thermometer at the beginning of the month varies from 72 to 74 °F (22 to 23 °C) at noon, and from the middle to the end gradually declines to 66 °F (19 °C) and sometimes to 60 °F (16 °C). In the mornings it is as low as 52 °F (11 °C), and fires become in consequence general throughout the colony.

The weather in the month of May is truly delightful. The atmosphere is perfectly cloudless, and the mornings and evenings become with the advance of the month more chilly, and render a good fire a highly comfortable and cheering guest. Even during the middle of the day the most violent exercise may be taken without inconvenience. The thermometer at sun-rise is under 50 °F (10 °C), and seldom above 60 °F (16 °C) at noon.

Winter

The three winter months are June, July, and August. During this interval the mornings and evenings are very chilly, and the nights excessively cold. Hoar frosts are frequent, and become more severe the further you advance into the interior. Ice 0.5 inches (1.3 cm) thick is found at the distance of 20 mi (32 km) from the coast. Very little rain falls at this season, but the dews are very heavy when it does not freeze, and tend considerably to preserve the young crops from the effects of drought. Fogs too are frequent and dense in low damp situations, and on the banks of the rivers. The mean temperature at day-light is from 40 to 45 °F (4 to 7 °C), and at noon from 55 to 60 °F (13 to 16 °C).

Spring

The spring months are September, October, and November. In the beginning of September the fogs still continue; the nights are cold, but the days clear and pleasant. Towards the close of this month the cold begins very sensibly to moderate. Light showers occasionally prevail, accompanied with thunder and lightning. The thermometer at the beginning of the month is seldom above 60 °F (16 °C) at noon, but towards the end frequently rises to 70 °F (21 °C)

In October there are also occasional showers, but the weather upon the whole is clear and pleasant. The days gradually become warmer, and the blighting north-west winds are to be apprehended. The sea and land breezes again resume their full sway. The thermometer at sun-rise varies from 60 to 65 °F (16 to 18 °C), and at noon is frequently up to 80 °F (27 °C).

In November the weather may be again called hot. Dry parching winds prevail as the month advances, and squalls of thunder and lightning with rain or hail. The thermometer at day-light is seldom under 65 °F (18 °C), and frequently at noon rises to 80 °F (27 °C), 84 °F (29 °C), and even 90 °F (32 °C).
— William Wentworth, Statistical, Historical, and Political Description of NSW

Classifications[]

Climate data[]

Temperature extremes[]

Highest minimum (Sydney CBD)^[10]

Rainfall extremes[]

Lowest monthly rainfall (Sydney CBD)^[10]

Lowest monthly rainfall (Prospect Reservoir)^[111]

See also[]

• Climate of Australia
• Geography of Sydney
• Environment of Australia
• Australian region tropical cyclone
• Climate change in Australia
• Effects of global warming on Australia

Notes[]

References[]

External links[]

Wikimedia Commons has media related to Weather events in Sydney.

• NSW and Sydney monthly climate summary archive
• NSW & Sydney seasonal climate summary archive
• NSW & Sydney annual climate summary archive
• Special Climate Statements