Climate of Sydney

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 half of the year and is at its lowest in the second half.[3] Precipitation varies across the region, with areas adjacent to the coast being the wettest.[4] The city receives around 20 thunderstorms per year.[5]

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

Sydney has 109.5 clear days and 127.2 cloudy days annually,[6][7] with the monthly percent possible sunshine ranging from 53% in January to 72% in August.[8] Sydney's heat is predominantly dry in spring, but usually humid in the summertime,[9] 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.[10][11] On some hot summer days, low pressure troughs increase humidity and southerly busters decrease temperatures by late afternoon or early evening.[12][13] In late autumn and winter, east coast lows can bring large amounts of rainfall.[14]

Sydney experiences an urban heat island effect,[15] making certain parts of the city more vulnerable to extreme heat, particularly the west.[15] 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.[16][17] The El Niño Southern Oscillation and the Indian Ocean Dipole[18] 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.[19][20][21][22]

Classifications
Sydney Climate according to major climate systems
Climatic scheme Initials Description
Köppen system[23][1] Cfa Humid subtropical climate
Trewartha system[24][25] Cf Subtropical humid climate
Alisov system[26] N/A Subtropical climate[lower-alpha 1]
Strahler system[27] N/A Moist subtropical climate
Thornthwaite system[28]
B1 B'2
 Humid and mesothermal
Neef system[29][30] N/A Humid climate of trade winds

Climate data
Climate data for Sydney (Observatory Hill)
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °C (°F) 45.8
(114.4)		 42.1
(107.8)		 39.8
(103.6)		 35.4
(95.7)		 30.0
(86.0)		 26.9
(80.4)		 26.5
(79.7)		 31.3
(88.3)		 34.6
(94.3)		 38.2
(100.8)		 41.8
(107.2)		 42.2
(108.0)		 45.8
(114.4)
Average high °C (°F) 27.0
(80.6)		 26.8
(80.2)		 25.7
(78.3)		 23.6
(74.5)		 20.9
(69.6)		 18.2
(64.8)		 17.9
(64.2)		 19.3
(66.7)		 21.6
(70.9)		 23.2
(73.8)		 24.2
(75.6)		 25.7
(78.3)		 22.8
(73.0)
Daily mean °C (°F) 23.5
(74.3)		 23.3
(73.9)		 22.0
(71.6)		 19.4
(66.9)		 16.6
(61.9)		 14.1
(57.4)		 13.4
(56.1)		 14.5
(58.1)		 16.9
(62.4)		 18.9
(66.0)		 20.4
(68.7)		 22.0
(71.6)		 18.8
(65.7)
Average low °C (°F) 20.0
(68.0)		 19.9
(67.8)		 18.4
(65.1)		 15.3
(59.5)		 12.3
(54.1)		 10.0
(50.0)		 8.9
(48.0)		 9.7
(49.5)		 12.3
(54.1)		 14.6
(58.3)		 16.6
(61.9)		 18.4
(65.1)		 14.7
(58.5)
Record low °C (°F) 10.6
(51.1)		 9.6
(49.3)		 9.3
(48.7)		 7.0
(44.6)		 4.4
(39.9)		 2.1
(35.8)		 2.2
(36.0)		 2.7
(36.9)		 4.9
(40.8)		 5.7
(42.3)		 7.7
(45.9)		 9.1
(48.4)		 2.1
(35.8)
Average rainfall mm (inches) 91.1
(3.59)		 131.5
(5.18)		 117.5
(4.63)		 117.1
(4.61)		 100.2
(3.94)		 144.7
(5.70)		 76.8
(3.02)		 75.4
(2.97)		 63.4
(2.50)		 67.7
(2.67)		 90.6
(3.57)		 73.0
(2.87)		 1,150.1
(45.28)
Average rainy days (≥ 1 mm) 8.2 9.0 10.1 8.1 7.8 9.2 7.1 5.6 5.8 7.6 8.7 7.9 95.1
Average afternoon relative humidity (%) 60 62 59 58 58 56 52 47 49 53 57 58 56
Mean monthly sunshine hours 235.6 202.4 213.9 207.0 195.3 177.0 204.6 244.9 237.0 244.9 228.0 244.9 2,635.5
Percent possible sunshine 53 54 56 61 59 60 65 72 66 61 55 55 60
Source 1: Bureau of Meteorology[7][31] (1991–2020 averages, records 1861–)
Source 2: Bureau of Meteorology, Sydney Airport (sunshine hours)[32]



Miscellaneous data for Sydney
Month January February March April May June July August September October November December Year
Average sea temperature °C (°F) 23.3
(73.9)		 23.7
(74.7)		 23.4
(74.1)		 22.7
(72.8)		 20.7
(69.3)		 19.3
(66.8)		 19.1
(66.4)		 18.8
(65.8)		 18.5
(65.3)		 19.2
(66.5)		 20.6
(69.0)		 21.9
(71.4)		 20.9
(69.6)
Mean daily daylight hours 13.5 13.4 12.4 11.3 10.4 10.0 10.1 10.9 11.9 13.0 13.9 14.4 12.1
Average Ultraviolet index 12 11 8 6 5 3 2 3 5 8 10 11 7.0
Source: Bureau of Meteorology (UV index)[41]
Source #2: Metoc (sea temperature) [42]

Temperature extremes
Highest monthly average temperature
Parameter Jan Feb March April May June July Aug Sept Oct Nov Dec
Sydney CBD[43]29.6 °C (85.3 °F)
(2017)		29.0 °C (84.2 °F)
(1998)		27.1 °C (80.8 °F)
(2006)		26.1 °C (79.0 °F)
(2018)		23.2 °C (73.8 °F)
(2014)		20.3 °C (68.5 °F)
(1957)		19.9 °C (67.8 °F)
(2018)		21.3 °C (70.3 °F)
(1995)		24.4 °C (75.9 °F)
(1988)		26.2 °C (79.2 °F)
(1988)		26.6 °C (79.9 °F)
(2019)		28.6 °C (83.5 °F)
(2005)
Bankstown Airport (Western Sydney)[44]32.3 °C (90.1 °F)
(2019)		30.8 °C (87.4 °F)
(2017)		28.8 °C (83.8 °F)
(1998)		27.8 °C (82.0 °F)
(2018)		23.4 °C (74.1 °F)
(2016)		19.7 °C (67.5 °F)
(2004)		20.0 °C (68.0 °F)
(2018)		21.9 °C (71.4 °F)
(1995)		25.4 °C (77.7 °F)
(2013)		27.6 °C (81.7 °F)
(1988)		28.6 °C (83.5 °F)
(2009)		30.8 °C (87.4 °F)
(2017)
Penrith (Far-West)[45]34.9 °C (94.8 °F)
(2019)		32.7 °C (90.9 °F)
(2004)		30.5 °C (86.9 °F)
(1998)		28.6 °C (83.5 °F)
(2018)		23.5 °C (74.3 °F)
(2016)		20.1 °C (68.2 °F)
(2004)		20.3 °C (68.5 °F)
(2018)		21.9 °C (71.4 °F)
(2009)		26.3 °C (79.3 °F)
(2013)		28.9 °C (84.0 °F)
(2013)		31.8 °C (89.2 °F)
(2009)		33.5 °C (92.3 °F)
(2019)
Lowest monthly average temperature
Parameter Jan Feb March April May June July Aug Sept Oct Nov Dec
Sydney CBD23.1 °C (73.6 °F)
(1948)		23.6 °C (74.5 °F)
(1860)		22.4 °C (72.3 °F)
(1870)		20.0 °C (68.0 °F)
(1893)		16.6 °C (61.9 °F)
(1898)		14.1 °C (57.4 °F)
(1887)		13.4 °C (56.1 °F)
(1896)		14.9 °C (58.8 °F)
(1943)		17.4 °C (63.3 °F)
(1889)		19.2 °C (66.6 °F)
(1903)		20.6 °C (69.1 °F)
(1943)		22.5 °C (72.5 °F)
(1924)
Prospect Reservoir (Western Sydney)[46]24.0 °C (75.2 °F)
(1965)		24.9 °C (76.8 °F)
(1966)		22.6 °C (72.7 °F)
(1967)		21.1 °C (70.0 °F)
(1983)		18.1 °C (64.6 °F)
(1968)		14.6 °C (58.3 °F)
(1968)		14.4 °C (57.9 °F)
(1966)		15.7 °C (60.3 °F)
(1967)		17.6 °C (63.7 °F)
(1966)		19.9 °C (67.8 °F)
(1966)		22.5 °C (72.5 °F)
(1971)		23.4 °C (74.1 °F)
(2011)
Highest minimum (Sydney CBD)[7]

Rainfall extremes
Highest daily rainfall
ParameterJanFebMarchAprilMayJuneJulyAugSeptOctNovDec
Sydney CBD[7]191.0 mm (7.5 in)
(17 Jan 1988)		243.6 mm (9.6 in)
(03 Feb 1990)		280.7 mm (11.1 in)
(28 Mar 1942)		191.0 mm (7.5 in)
(29 Apr 1860)		212.3 mm (8.4 in)
(28 May 1889)		150.6 mm (5.9 in)
(11 Jun 1991)		198.1 mm (7.8 in)
(07 Jul 1931)		327.6 mm (12.9 in)
(06 Aug 1986)		144.5 mm (5.7 in)
(10 Sep 1879)		161.8 mm (6.4 in)
(13 Oct 1902)		234.6 mm (9.2 in)
(28 Nov 2018)		126.0 mm (5.0 in)
(14 Dec 1991)
Western Sydney (Prospect Reservoir)[40]161.2 mm (6.3 in)
(31 Jan 2001)		165.0 mm (6.5 in)
(10 Feb 2020)		153.9 mm (6.1 in)
(20 Mar1892)		163.1 mm (6.4 in)
(16 Apr 1946)		314.2 mm (12.4 in)
(28 May 1889)		163.4 mm (6.4 in)
(11 Jun 1991)		143.5 mm (5.6 in)
(10 Jul 1904)		321.0 mm (12.6 in)
(06 Aug 1986)		96.5 mm (3.8 in)
(02 Sep 1970)		102.1 mm (4.0 in)
(05 Oct 1916)		126.2 mm (5.0 in)
(14 Nov 1969)		154.9 mm (6.1 in)
(13 Dec 1910)
Lowest monthly rainfall (Sydney CBD)[7]
Lowest monthly rainfall (Prospect Reservoir)[40]

Seasons

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

Summer in Sydney tends to vary, but it is generally warm to hot.[47] The western suburbs are significantly hotter than the Sydney CBD by 2–5 °C (4–9 °F) due to urban sprawl exacerbating the urban heat island effect and less exposure to mitigating sea breezes. In extreme occasions, the coast would have a temperature of 25 °C (77 °F) with a sea breeze, while a suburb 30 km (19 mi) inland bakes in 38 °C (100 °F) heat. At times, sea breezes do eventually reach the inland suburbs later in the day and 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.[7]

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%.[7][48] 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.[49]

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,[50] 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.[51][52]

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).[7] 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.[48][53] 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.[54] The highest recorded minimum at Observatory Hill is 27.6 °C (81.7 °F), registered on 6 February 2011.[7] A similar minimum temperature has also been recorded in the western suburbs.[48]

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.

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.[55]

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.[48] The lowest maximum temperature in autumn is 11.3 °C (52.3 °F), recorded on 24 May 1904.[7]

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.[56] Winter in central Sydney tends to be more mild where the lows rarely drop below 7 °C (45 °F), and highs hovering at around 16 ° C (61 ° F) and 17 ° C (63 ° F) mainly due to proximity to the ocean.[7]

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.[48] 9am humidity ranges from 61% to 74% across the Sydney region, with the more higher figures experienced in June mornings.[7][48]

Fog is common in winter mornings, namely in June when moist easterlies dominate. The western suburbs are more prone to fog than the Sydney CBD. Heavier rain and cloudiness are also to be expected more in June, on average, than the latter winter months. Highs of 12 °C (54 °F), whilst rare, are not unheard of in winter.[57] During late winter, warm dry westerly winds which dominate may raise the maximum temperatures as high as 30 °C (86 °F) in some instances. The dry westerlies also bring more sunny days, hence why August has the highest sunshine percentage than any other month.[58]

The lowest recorded minimum at Observatory Hill was 2.1 °C (35.8 °F) on 22 June 1932,[7] 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.[59]

Spring
Jacaranda trees bloom ostentatiously in springtime, where they attract sightseers and photographers.[60]

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.[61]

Spring generally tends to be mostly sunny, warm and dry 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.[56]

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).[62] 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.[7]

The lowest maximum temperature in spring was 9.5 °C (49.1 °F), recorded on 8 September 1869.[7] 9am relative humidity is the lowest in the year during spring, ranging from 58% to 68%, with early spring receiving lower figures.[48]

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.[63][64]

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).[65]

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.[66] 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,[67][68] with September being one of the driest. In September, temperatures were 4 °C (7 °F) above average[69] and the city had over seven days where temperatures reached 28 °C (82 °F), making it more similar to November's weather pattern.[70] October 2015 had the warmest nights on record, which were 3.3 °C (5.9 °F) above average.[71] The warming trend continued in 2016 as Sydney's warmest autumn ever was recorded.[72] 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.[73]

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.[74] On 7 January 2018, Sydney was the hottest place on Earth.[75] 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.[76] 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.[77]

Precipitation
See also: Severe storm events in Sydney
Rain falls on Martin Place, 1937.
Due to their elevation, the Northern Suburbs and The Hills Shire create an orographic rainfall, making them wetter and cooler than the rest of the Sydney Basin.[78]

Rainfall is fairly evenly spread through the year, with moderate to low variability, though it is slightly higher during the first half of the year when easterly winds dominate (February–June) and lower in the second half (mainly July–September).[79][80] Due to the unpredictability of rain, the wettest and driest months would change on a yearly basis.[81] Within the city and surrounds, rainfall varies, from around 700 mm (27.56 in) at Badgerys Creek[82] (in the west) to 1,400 mm (55.12 in) at Turramurra (the northeast).[83]

Rain hours are longer in the winter than in the summer, with rainfall lingering on for the whole day. In some cool days, rain may come in drizzle form. In the warm months, rain comes in short heavy downpours in the afternoons, usually cooling the conditions and providing some respite.[84] Sometimes these afternoon showers give away to the sun again, although black nor'easters may provide rainfall for a few consecutive days.[85][7][48] 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).[86]

In the cool months, the Sydney CBD is more prone to rain than the inland suburbs, mainly due to the wonted east coast low that strikes between the months of May and August. The low would usually dump more rain in the CBD than the inland areas, usually by 20 mm (0.79 in) or more. 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 are more inclined to have heavy rain and thunder in the summer.[87]

The city is rarely affected by cyclones, although remnants of ex-cyclones do affect the city.[88] 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.[89][90]

The annual evaporation rate for Sydney is 1,600 mm (62.99 in),[91] with the rate in the summer being 600 mm (23.62 in)[92] and in winter 300 mm (11.81 in).[93]

Snowfall

Snow is extremely rare in Sydney and was last reported in the Sydney area in 1836. T. A. Browne, who kept weather observations, noted that "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 Herald reported on the same incident, 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."[94]

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.[95]

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 though, 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.[96] It is extremely rare to see snow below Lawson.[97]

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).[7] 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.[98]

Northeasterlies and easterly sea breezes are dominant in late spring to early autumn. Westerlies are dominant in late winter to mid-spring. Southerly busters are expected from November to the end of February. 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.

When the subtropical ridge is north of Sydney in the second half of the year (spring), the wind would come from the west or inland. As the ridge moves south in late summer and autumn, the winds become easterly and, because they are coming off the Tasman Sea, they are moist. It is usually at this time of the year (autumn to early winter) where rainfall would be the highest.[99][100]

Wind direction in Sydney from 2002 to 2012 (average values)
North Northeast East South East Southern Southwest West Northwest
5.9% 16.9% 14.1% 14.6% 24.9% 4.1% 11.9% 7.6%
Source: world-weather.info

Föhn effect
Föhn wind illustration (Left: Blue Mountains, Right: Sydney).

Since Sydney borders the Blue Mountains (part of the Great Dividing Range), it would experience a Föhn-like type of wind,[101] which is a dry 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.[102]

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, typically in spring, due to their dry, gusty nature.[103][104]

In winter, 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.[105] These southwesterly 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 from the southwest of the continent, usually strengthened by the roaring forties,[106] and a deep low pressure system.[107] Typically occurring in late winter and early spring, the winds would usually cause heavy snowfall and sleet in the mountains, but would provide clear and relatively warmer conditions on the lee side of the mountain range in the Sydney region.[108]

Katabatic flow

Katabatic winds are southwesterly 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. They are generally light and unobtrusive, and would tend to arrive during nighttime, usually in the winter.[109][110][111]

Drought
See also: Federation Drought, 1979–83 Eastern Australian drought, and 2000s Australian drought
Smoke from bushfires around Sydney, January 1994.

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.[112][113][114]

The years 2009 and 2010 had dry conditions, according to Bureau of Meteorology.[115] 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.[116] It stretched as far north as southern Queensland and it was the worst dust storm in 70 years.[117] During that year, Sydney experienced a number of warm winter days, dry gusty winds and another milder dust storm.[118][119]

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.[120] 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.[68] 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.[121]

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.[122] 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.[123]

Furthermore, 2018 in Sydney has been one of the driest in a century, with the Greater Western Sydney farming region being the worst affected.[124] 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,[125][126] even making it worse than New Delhi's,[127] where it was also equalled to "smoking 32 cigarettes."[128] 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.[129]

Aboriginal seasons

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:[130]

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

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Notes
  1. Subtropical oceanic climate
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