Severe flooding in Tasmania has triggered evacuation orders as police launched a rescue mission for stranded walkers on snow-capped Mount Wellington amid wild weather lashing southern Australia.
Bushfires also threatened properties in NSW and wild winds caused almost 100 flights to be cancelled at Sydney airport.
The extreme weather, which began on Sunday night, resulted in the death of a 63-year-old woman after a tree struck a cabin at a holiday park in Moama, on the NSW-Victoria border.
More than 120,000 Victorians are without power and 660 homes have been damaged following a night of pulsing winds and abnormally high tides, with some schools and kindergartens forced to close.
Strong winds of up to 85km/h caused the cancellation of 90 flights to and from Sydney Airport with just one of its three runways in use.
Tasmania Police have launched a rescue operation for a group of walkers who became stranded on a hard-to-reach section of Mount Wellington in Hobart.
"We can't guarantee that we'll always be able to rescue stranded walkers so visiting the mountain in these extreme weather conditions comes with high risk," City of Hobart chief executive Michael Stretton said.
Temperatures on the snowy mountain have been below -3°C while wind gusts reached up to 109km/h.
Tasmania SES executive director Mick Lowe said the service fielded more than 340 requests for assistance in 24 hours.
Evacuation warnings have been issued for residents in the Derwent River, Meadowbank to Macquarie Plains and Styx River, Bushy Park to Macquarie Plains and surrounds.
"That is significant for a small jurisdiction like ours - we have had to be careful," Mr Lowe said.
"If you're out on the roads, the message is simple - if it's flooded, forget it.
"Never enter or drive through floodwaters."
TasNetworks said about 10,000 customers were without power.
In NSW, a bushfire near Wollongong closed the M1 on Princes Highway and two lanes on the M4 for several hours on Monday afternoon.
Another blaze was burning out of control in Tomago north of Newcastle, with residents told to prepare their homes.
Victoria's State Emergency Service received 2800 calls for help between 7pm Sunday and 10am Monday, 1350 of them related to fallen trees.
Warragul, Moe and Emerald were the worst-affected areas.
The state's emergency services have warned against unnecessary travel after winds brought down trees and powerlines, reaching 146km/h at Wilsons Promontory National Park.
Gusts of more than100km/h were also recorded in suburban Melbourne, including 113km/h at St Kilda.
Numerous schools lost power and some including St Helena Secondary College in Eltham and Yarra Ranges Special Developmental School closed, with students directed to undertake remote learning for the day.
A severe weather warning is still in place in parts of Victoria, with residents urged to prepare for another storm front expected to hit on Monday night.
Peak wind gusts in Tasmania on Sunday night reached 157km/h at King Island Airport and 130km/h at Launceston Airport.
The River Derwent, below Meadowbank Dam, was likely to exceed the major flood level of 7.3 metres on Monday, while emergency services warned those in White Hills, near Launceston, to remain vigilant.
NSW police will prepare a report for the coroner following the woman's death after a tree landed on a cabin she was staying in at holiday park at Merool on the Murray.
A man, also aged 63, was taken to hospital with minor injuries.
