The climate of Sydney is humid subtropical (Köppen Cfa), 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. More contrasting temperatures are recorded in the inland western suburbs. Although 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. Precipitation varies across the region, with areas adjacent to the coast being the wettest. The city receives around 20 thunderstorms per year.
Sydney has 103.9 clear days annually, with the monthly percent possible sunshine ranging from 53% in January to 72% in August. Sydney's heat is predominantly dry in spring, but usually humid in the summertime, 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. In some hot summer days, low pressure troughs would increase humidity and southerly busters would decrease temperatures by late afternoon or early evening. In late autumn and winter, east coast lows can bring large amounts of rainfall.
Sydney experiences an urban heat island effect, making certain parts of the city more vulnerable to extreme heat, particularly the west. 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. The El Niño Southern Oscillation plays 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 recent years.
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Climate data
Seasons
Summer
Summer in Sydney tends to vary, but it is generally warm to hot. The western suburbs are significantly hotter than the Sydney CBD by 2-5 °C (4-9 °F) due to industrialisation and proximity to the dry, hot inland desert region. 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 extremities would occur. The far-western suburbs, which lie on the foothills of Blue Mountains, have a Föhn effect originating from the Great Dividing Range. The lifting of the warm, dry winds originating from Central Australia over the Blue Mountains forces the air to descend into the Sydney basin, where it would become hotter by the time it reaches the Sydney basin (providing it isn't cooled by the sea breeze further east).
When temperatures reach over 30 °C (86 °F), the relative humidity would seldom exceed 45%, although low pressure troughs would increase humidity in some hot days, especially in late summer. Furthermore, most mornings and nights would still be muggy, with the 9am relative humidity ranging from 69% to 75%. 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 9C in the extremely hot day.
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, although they are often ended with a Southerly Buster, which is a cold front that sweeps up from the southeast abruptly cooling the temperature. At times, this cold front would bring thunderstorms, rainfall and gale winds.
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). 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. 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. The highest recorded minimum at Observatory Hill is 27.6 °C (81.7 °F), registered on 6 February 2011. A similar minimum temperature has also been recorded in the western suburbs.
Autumn
Late summer conditions continue until the last few weeks of March 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 affect by around April. In mid-autumn, the highs typically average at a pleasant 23 °C (73 °F), rarely going above 26 °C (79 °F) or below 20 °C (68 °F). In May, the average highs would be around 22 °C (72 °F) and 19 °C (66 °F) with cool and usually humid nights, that seldom dip below 10 °C (50 °F). Wintry highs of 17 °C (63 °F) may be expected in the last week of autumn.
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. The lowest maximum temperature in autumn is 11.3 °C (52.3 °F), recorded in 24 May 1904.
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 nights. Such low temperatures may provide mild to moderate frost in the western suburbs. Winter in central Sydney tends to be more mild where the lows rarely drop below 7 °C (45 °F), mainly due to proximity to the ocean.
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. 9am humidity ranges from 61% to 74% across the Sydney region, with the more higher figures experienced in June mornings.
Fog is common in winter mornings, namely in June when moist easterlies dominate. The western suburbs are more prone to fog than 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. 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.
The lowest recorded minimum at Observatory Hill was 2.1 °C (35.8 °F) on 22 June 1932, 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.
Spring
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.
Spring generally tends to be mostly be sunny, warm and dry with the temperatures averaging at around 21 °C (70 °F) and 25 °C (77 °F) with relatively low dewpoints, hovering around 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.
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). 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.
The lowest maximum temperature in spring was 9.5 °C (49.1 °F), recorded in 8 September 1869. 9am relative humidity is the lowest in the year during spring, ranging from 58% to 68%, with early spring receiving lower figures.
Warm and cool periods
The Bureau of Meteorology has reported that 2002 through 2005 were the warmest summers 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 on 151 years of record have occurred in the ten years between 2001 and 2010, with this decade being the warmest on record for minimum temperatures.
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).
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 seventh highest annual average maximum temperature since records commenced in 1859. 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, with September being one of the driest. In September, temperatures were 4 °C (7 °F) above average and the city had over seven days where temperatures reached 28 °C (82 °F), making it more similar to November's weather pattern. October 2015 had the warmest nights on record, which were 3.3 °C (5.9 °F) above average. The warming trend continued in 2016 as Sydney's warmest autumn ever was recorded.
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 (35.1 °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. On 7 January 2018, Sydney was the hottest place on Earth.
Precipitation
Rainfall is fairly evenly spread through the year, with moderate to low variability. Precipitation 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). Due to the unpredictability of rain, the wettest and driest months would change in a yearly basis. Within the city and surrounds, rainfall varies, from around 700 mm (27.56 in) at Badgerys Creek (in the west) to 1,400 mm (55.12 in) at Turramurra (the northeast).
Rain hours are longer in the winter than in the summer. In the warm months, rain comes in heavy downpours in the afternoons, usually cooling the conditions. Sometimes these afternoon showers give away to the sun again. In the cool months, the rain is moderate and it would linger on for the whole day. In some days, rain may come in drizzle form. Even in its months of highest rainfall Sydney has relatively few rainy days, on average less than 13 rainy days per month.
In the cool months, 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.
The city is rarely affected by cyclones, although remnants of ex-cyclones do affect the city. 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 (during autumn-winter periods) and ex-tropical cyclone remnants (during summer periods). 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.
Notable events
A notable event was the great Sydney flood which occurred on 6 August 1986 (unusual in that month) and dumped a record 327.6 mm (12.90 in) on the city in 24 hours. This caused major traffic problems and damage in many parts of the metropolitan area. The next notable event was the 1999 hailstorm, which caused severe damage in many suburbs. The storm produced hailstones of up to 9 cm (3.5 in) in diameter and resulted in insurance losses of around A$1.7 billion in less than five hours.
In February 2010, Sydney received some of the highest rainfalls in 25 years with 65 mm (2.6 in) of rain falling in one night at Observatory Hill. In the first weeks of the month, some suburbs were hit by thunderstorms which brought heavy rain and gusty winds which cut out power and damaged homes. The heavy rain was caused by remnants of ex-tropical Cyclone Olga and humid north-easterly winds feeding into the low pressure trough. 2010 was an overly wet year with the cloudiest October and the third cloudiest July on record. In 2011, Sydney recorded its wettest July since 1950. The CBD recorded 244 mm (9.61 in) of rain that month. 2011 was also the wettest year since records began in 1858.
On 18 November 2013, a tornado hit Hornsby, a suburb in the Upper North Shore. The tornado's path was 2 km (1.2 mi) long and 50 m (160 ft) wide. The tornado blew off roofs and toppled large trees. The winds in the tornado reached 140 kilometres per hour (87 mph). A total of 12 people were injured in the tornado.
On 15 October 2014, a rainstorm described as a "once-in-a-decade event" hit the Sydney region. Parts of Sydney received the heaviest amount of rain in a span of hours in decades. 94 mm (3.70 in) of rain fell in Strathfield in just over three hours. The winds were cyclonic in nature, with Sydney Airport having over 107 km/h (66 mph) gusts, reaching category 1 strength. This event happened due to the formation of an east coast low, which ignited several other low pressure systems.
On 20 April 2015, Sydney recorded 119.4 mm (4.70 in) of rainfall, the most in any day since February 2002. Winds were "cyclonic" in nature, reaching 135 km/h (84 mph). This east coast low was formed with "a really pronounced upper level trough of cold air that had moved in from Victoria", Mr Sharpe said. The maximum temperature was only 15.4 °C (60 °F), making it the coldest April day since 1983, according to BOM.
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." A July 2008 fall of graupel, or soft hail, mistaken by many for snow, has raised the possibility that the 1836 event was not snow.
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 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. It is extremely rare to see snow below Lawson.
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). 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.
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.
Drought
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. The years 2009 and 2010 had dry conditions, according to Bureau of Meteorology. On 23 September 2009, a dust storm that started in South Australia and inland New South Wales blanketed the city with reddish orange skies. It stretched as far north as southern Queensland and it was the worst dust storm in 70 years. During that year, Sydney experienced a number of warm winter days, dry gusty winds and another milder dust storm.
In 2011, Sydney had the driest February in 30 years with only 18 mm (0.71 in) of rain falling, which is well below than the average 118 mm (4.6 in). Some of the western suburbs recorded the lowest total February rainfall on record. 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.
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. 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.
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 in hot days, even without bushfires.
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:
- 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
Source of the article : Wikipedia
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