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 as the weather is moderated by proximity to the ocean,^[3] 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 during summer and autumn months,^[2] and is at its lowest just around the middle of the year, though precipitation can be erratic throughout the year.^[6][7] Precipitation varies across the region, with areas adjacent to the coast being the wettest.^[8] According to the Bureau of Meteorology, Sydney falls in the temperate climate zone which has warm to hot summers^[a] and no dry season.^[9][10] Sydney's plant hardiness zone ranges from zone 11a to 9b throughout the metropolitan area.^[11] Under the Holdridge Life Zones classification, eastern Sydney falls in the Subtropical Moist Forest zone and the western suburbs in the Subtropical Dry Forest zone.^[12]

Sydney has 109.5 clear days and 127.2 cloudy days annually,^[13] though it has around 200 days of visible sunshine if partly cloudy days or sunny breaks are counted.^[14] 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.^[15] Sydney's heat is predominantly dry in spring, but usually humid in the summertime.^[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 the warm season, particularly late summer and early autumn, troughs combined with a humid air mass can bring large amounts of rainfall,^[19] and in late autumn to early winter, the city can be affected by east coast lows.^[20] When the subtropical ridge is north of Sydney in late winter to early spring, the wind comes from the west or inland. As the ridge moves south in summer and autumn, the winds become easterly.^[21][22][23]

Sydney experiences an urban heat island effect,^[24] making certain parts of the city more vulnerable to extreme heat, particularly the west.^[24] 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.^[25][26] The El Niño Southern Oscillation, the Indian Ocean Dipole and the Southern Annular Mode^[27][28] 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.^{[29][30][31][32]} Furthermore, the region of Sydney, and as well as the rest of the New South Wales coastline, is warmed by the East Australian Current.^[33][34] 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.^[35] In 2023, Sydney was placed at 9th place by Stars Insider for having the best weather in the world.^[36]

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