Sydney has recorded its coldest November night in 20 years after a polar cold front swept across south-eastern Australia, dumping about 10 centimetres of snow on the New South Wales and Victorian alps just weeks before summer. The unseasonable blast brought frosts, hail and thunderstorms to a region more used to late-spring warmth.

The temperature in Sydney fell to about 9.7 degrees Celsius, the city's coldest November night in two decades, according to Weatherzone. The drop capped a dramatic Saturday in which the city went from a warm 29 degrees in the morning to about 14 degrees by early evening, when a thunderstorm brought hail and high winds.

Snow in the alps

Alpine regions of New South Wales and Victoria saw about 10 centimetres of snowfall, with stunned tourists and locals taking to social media to document the snow. Perisher received about 10 centimetres on Saturday afternoon, and snow was recorded in Cooma, Jindabyne and Thredbo, with resort snow cameras showing a solid cover still in place on Sunday morning.

The cold was at its sharpest in the mountains. Minima recorded on Sunday morning included minus 5.9 degrees at Mount Hotham, minus 5.6 degrees at Falls Creek and minus 5.1 degrees at Perisher Valley. Snow was forecast down to about 400 metres in Tasmania and 800 metres in parts of Victoria and the New South Wales alps, and snowflakes fell as low as 1,000 metres above sea level during heavy showers on Saturday afternoon.

Sydney did not climb above 20 degrees on Sunday, with the wind chill making it feel like about 8 degrees on Sunday morning. Bureau of Meteorology senior meteorologist David Crock said on Sunday that the weather was uncommon for this time of year, but not entirely unprecedented.

Warnings and the warm-up

Warnings remained in place on Monday morning for parts of New South Wales and Victoria, with ongoing cold temperatures that could threaten livestock, although further snowfall was not expressly forecast. Temperatures again plunged below zero on Monday morning in Victoria, New South Wales, Tasmania and the Australian Capital Territory.

The chill is not expected to last. Melbourne was forecast to surge to 27 degrees by Wednesday, and Sydney was expected to sit in the early to mid-20s for most of the week, with Monday struggling to break above 21 degrees. For a weekend, though, south-eastern Australia got a reminder that spring in the alps can still turn wintry — with more snow falling in a single front than many fronts delivered all last winter.