In short:
Minimum temperatures dropped below 0 degrees Celsius in some parts of southern Australia overnight.
Liawenee in Tasmania was the coldest place in Australia, dropping to minus-12.9C — the lowest recorded across the country.
What's next?
The Bureau of Meteorology said conditions were expected to improve across south-eastern Australia on Friday and the weekend.
Freezing conditions have sent weather records tumbling in suburbs and towns across southern Australia overnight.
Residents across much of the south-east woke up to cold weather and frost.
Liawenee in Tasmania was the coldest place in the country, dropping to minus-12.9 degrees Celsius.
It was the lowest temperature recorded in Australia so far this year, according to the Bureau of Meteorology (BOM).
The cold conditions extended over Victoria and South Australia.
Adelaide was the coldest capital on Wednesday morning, dipping to 0.6C at 7:35am.
The last time the city's West Terrace station recorded the same minimum temperature was on July 25, 1908 but the Kent Town site, east of the CBD, observed 0.2C in June 15, 2006.
Nullarbor, near the SA-WA border, recorded its lowest minimum temperature since records began with minus-3.2C.
Melbourne recorded its coolest temperature since 2022, with a minimum of 1C on Wednesday morning, while surrounding suburbs dropped below zero.
Omeo, in Victoria's East Gippsland, dropped to minus-4.1C and Coldstream, in the Yarra Valley, dropped to minus-3.9C.
BOM senior forecaster Angus Hines told the ABC the cold snap was caused by a cold front that crossed southern Australia at the weekend.
Mr Hines said that made way for a high pressure system that settled conditions and cleared skies which caused temperatures to drop.
"Quite a strong cold front that crossed over southern and much of eastern Australia during last weekend. [It] brought some rain, it brought some strong winds, it brought some cloudy skies and it does bring the cold air in," Mr Hines said.
"We often find that with cold fronts like that, that the coldest days actually arrive a few days after the front has passed … and then we get high pressure areas.
"That's because the initial front moves through, brings all the weather and then it moves away but the cold conditions come in behind."
Mr Hines said residents in Victoria, South Australia and Tasmania woke up to thick frost on Wednesday that would have taken hours to thaw.
"You can even see the frost on some satellite imagery showing how extensive it is. The broad areas of whiteness covering the land during the first hour or so after sunrise before that frost really thaws."
He said conditions were expected to improve across the south-east on Friday for the weekend.
"Tomorrow is likely to be another chilly morning across the south east but maybe not quite as cold for Adelaide, but Melbourne and Tasmania could see a day of similar temperatures to what they saw this morning, potentially a shade colder here and there."