State Emergency Services are dealing with the aftermath of line of severe storms that stretched from southern Queensland, through NSW down to Echuca in central Victoria.
There are reports of tornadoes, hail and flooding and Bureau of Meteorology senior forecaster Richard Carlyon said at least one of the suspected tornadoes was confirmed.
"This was a very broad line of storms, that extended basically from Queensland down towards Gippsland," Carlyon told The Huffington Post Australia.
"It's rare to see a storm line stretch that far. It can happen, you need a very active low pressure trough to extend right through that distance."
He said that while residents of the small town of Strathmerton believed a tornado had swept through, it looked to be unlikely.
"It looks as though about 10 houses lost their roofs all on the one street," Carlyon said.
"Looking at the radar, the indication is that it wasn't a tornado, it was strong down bursts out of the thunderstorm.
"We did record gusts of 90kmph in Shepparton and 117kmph in the southern NSW town of Hay."
Further south, however, Carlyon said there did appear to have been a tornado.
"There's strong evidence that there was a tornado in a place called Nathalia -- south of Strathmerton," he said.
"They're not particularly common in Victoria, we probably get about one to three reports of a tornado a year and with spring coming, this is getting towards the time of year when they occur."
A Victoria State Emergency Service spokeswoman told HuffPost Australia there had been 120 call-outs for help across the state on Sunday afternoon, with roughly 20 for property damage and about 35 for fallen trees blocking roads, or power lines.
In Sydney, meanwhile, golf ball-sized hail pelted the city from Bankstown to Wollongong.
The storms were expected to become less severe overnight.