The Bureau of Meteorology says snow is forecast for the Adelaide Hills and South Australia's mid-north on Tuesday, while up to 80mm of rain could cause flooding in the hills.
Severe weather has battered the state's hills and coastal regions from late on Monday, bringing down trees and causing widespread minor damage.
About 30,000 properties across South Australia are without power after a night of fierce winds and rain.
Wind gusts hit 139km/h at Cape Willoughby on Kangaroo Island where there have been widespread blackouts.
Port Lincoln recorded a gust of 113km/h, Hindmarsh Island reached 109km/h and Kingscote and Cape Jaffa 111km/h.
The State Emergency Service has already taken almost 200 calls for help so far on Tuesday, on top of the more than 500 from Monday.
The Bureau of Meteorology says the conditions will persist over South Australia well into Tuesday.
A severe weather warning remains in place for most coastal regions and for the Mt Lofty Ranges.
There are also warnings in place for cold temperatures, raid and strong winds across large parts of NSW.
A flood watch for the Adelaide Hills and the mid-north also remains in force where some light snow is also possible.
The bureau expects up to 80mm of rain to fall in some parts of the hills while Adelaide is tipped to get a more reasonable 10mm with a top temperature of just 11C.
There have been no reports of injuries so far on Tuesday.
However, on Monday, a 71-year-old man was killed when he was crushed by a falling tree at Tungkillo, in the Adelaide Hills.
Several other people also suffered minor injuries from falling trees and other debris, including one man who had a lucky escape when a large tree crushed the roof of his car.
Dozens of trees were brought down across Adelaide and the Mt Lofty Ranges, including several which blocked roads.
Victoria battered
A tin roof has been blown off a house, a trailer detached from a truck and large trees ripped from their roots as wild winds blast Victoria.
The Bureau of Meteorology has warned damaging thunderstorms, hail and strong winds are on the way as a low pressure system sweeps across the state, sending temperatures plummeting.
The SES has received more than 170 calls for help across the state before midday (AEST) on Tuesday and says those most affected are along the Bellarine and Mornington peninsulas.
Tin sheeting was blown off a roof in Geelong and a trailer detached from a truck on the Geelong Freeway.
Crews are also working to remove a large tree from a home in Belgrave with reports of a number of trees down over roads in the Dandenong Ranges.
"Predominantly (the reports) are trees down and building damage as a result of trees falling," SES state agency commander David Baker said on Tuesday.
And the worst is yet to come, with senior meteorologist Adam Morgan warning areas including the Dandenong Ranges and Arthurs Seat could see snow fall early on Wednesday.
He said Victorians could expect to experience the weather in two parts - strong winds on Tuesday and freezing conditions on Wednesday.
"Wind chill is expected to be extreme through Melbourne (on Wednesday). It will feel like zero through most of the day," Mr Morgan told reporters on Tuesday.
He said reports that snow could fall in the suburbs were unlikely - especially in the city.
"You might catch a snow flake or two at the top of the Eureka Tower or Rialto but the snow is not likely to come through - the best chance will be for a light flurry in the outer east or southeastern suburbs where we're more likely to see showers," he said.
The SES are warning the public to drive to the conditions and look out for hazards such as fallen trees and black ice.
