Climate of Sydney

The climate of Sydney, Australia is humid subtropical (Köppen: Cfa),[1] shifting from mild[2][3][4] and cool[5] in winter to warm and occasionally hot[5] in the summer, with no extreme seasonal differences since the weather has some maritime influence.

[10] In the February 1938 issue of The Home, journalist Basil Burdett wrote, "...Even Melbourne seems like some grey and stately city of Northern Europe compared with Sydney's sub-tropical splendours.

[12] According to the Bureau of Meteorology, Sydney falls in the temperate climate zone with warm to hot summers[a] and no dry season.

[19] 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, in addition to the city being sunny around 65% of the time in the year with its 2,640 hours of annual sunshine.

[25] 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.

[34][35] In 2020, researchers at The Australia Institute discovered that Sydney was experiencing longer summers and shorter winters in recent decades, compared to those in the 1950s and 1960s.

On these occasions, the city can experience the fury of the desert climate,[42] although they are often ended with a southerly buster, which is a windy, shallow cold front or a sea breeze that sweeps up from the southeast abruptly cooling the temperature.

[46] Sydney receives around 15 days of fog annually,[53] which occurs in winter mornings; some can be thick enough to divert planes and cancel ferry services.

[54][55] During late winter, warm dry westerly winds which dominate may raise the maximum temperatures as high as 25 °C (77 °F) in some instances.

As the subtropical ridge is north of Sydney in mid-to-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.

Cool conditions from late winter may continue in September, but due to the drastic transition, temperatures above 30 °C (86 °F) can also be expected in that month, including the odd thunderstorm.

[60] 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,[28][50] with relatively low dewpoints.

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.

[78] Because 48.9 °C (120.0 °F) was recorded in Penrith (on 4 January 2020), it will not 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.

[72] According to climate researchers, relatively easy modifications such as constructing fountains and water playgrounds could also lower temperatures in the western suburbs.

[84][85] Rainfall is slightly higher or dominant during the first half of the year, particularly in late summer and early autumn, when the ocean has peaked its warmth.

[50][87] Most rain comes mostly from major storms, rarely drizzle, particularly from subtropical lows that bring warm, moist air onshore.

Coastal showers, which are mostly stratiform, occur in post-frontal south-east flow, where they become volatile over the warm ocean near Sydney, thereby setting up an "ocean-effect" (where rainfall is intensified leeward of a waterbody).

[89] Therefore, the drier winters are due 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.

[96] East coast lows, which strike from the southeast in the Tasman Sea, bring heavy rainfall typically in autumn to early winter.

[89] Annually, there are around 40 days with convective thunderstorms, which particularly occur in late spring and summer – Such storms arrive from the west, and normally involve northeasterly winds at the surface.

The other phenomenon that arises from these long, dry and hot periods is bushfires, which occur frequently in the areas surrounding the city.

Heatwaves, which are regularly occurring in recent years, usually lead to water restrictions and a high risk of bushfires, which sometimes bring a smoky haze to the city.

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.

[125][126][127] Since Sydney is located on the Great Dividing Range's eastern side, and is thus in its rain shadow,[b] it experiences a föhn-like type of wind, particularly between late autumn and early spring, which is a dry south-westerly that raises the air temperature and provides clear to partly sunny conditions in the lee of the mountains (in this case, the Sydney Basin), after the arrival of a vigorous westerly cold front from the Southern Ocean.

[134] In 1819, British explorer William Wentworth describes Sydney's climate:[135] Below, Wentworth describes Sydney's[d] seasonal and annual weather patterns in analytical detail:[135] 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.

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 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.

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.

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.