A blast of cold from the Antarctic is set to hit several states this week, bringing wintry and dangerous conditions.
In NSW, the Bureau of Meteorology is warning of heavy rains and snow down to 900 metres, while in Victoria, forecasters are warning of destructive winds and rainfall of up to 250 millimetres.
NSW bureau forecaster Hugh McDowell said the "cold air outbreak" would mean difficult weather conditions.
"It's coming up from Antarctica, it is changing on the way, but it is quite unusual for it to be this cold," he told AAP.
In NSW snow is likely down to 1000m on Monday night, while on Tuesday a developing low pressure system will bring the risk of flash flooding in parts of the state, as well as potentially damaging winds in the tablelands and the alps, and snow down to 900m.
Places such as Orange, Oberon, the Blue Mountains, Armadale and Glen Innes, and even Canberra, Cooma and Goulburn could see a sprinkling of snow as temperatures drop well into single digits.
There could even be snow in Queensland across the Darling Downs.
Tuesday is expected to be the coldest day of the week for towns in South Australia and western Victoria, while most towns across NSW and the ACT will see the lowest temperatures on Wednesday.
For those in south-east Queensland, the coldest day is likely to be Thursday.
Weather could get "quite dangerous"
The bureau is warning of black ice on the roads in parts of NSW, and says people should not drive unless they have to.
Extreme weather is on the way in Victoria too.
Forecaster Tom Delamotte told AAP the cold weather system would be "quite dangerous" in Victoria on Wednesday and Thursday.
"When the east coast low brings strong winds and pushes into Gippsland, we could see damaging and destructive winds and very heavy rainfall," he told AAP.
Parts of the state could see rain of up to 250mm, with the risk of flooding.
He said while these types of weather systems were usually felt on the NSW coast, this time Gippsland, and Victoria's central highlands and alpine region would also feel the brunt.
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