Weather in Sydney, Brisbane, Melbourne: Worst floods in decades hit Victoria, as scorching heatwave looms for other parts of Australia

Australians in the south-east of the country are dealing with the worst flooding they have seen in decades, while residents in the west are dealing with an extreme heatwave.

Heavy rain on Monday has caused major flooding in Victoria, with warnings that river levels will remain high over the coming days.

Dozens of calls for help have already been made, while authorities have warned residents of the central region that it is too late to leave their homes as floods approach.

The wet weather system has moved further, bringing showers and thunderstorms to northeastern NSW and southeastern Queensland on Tuesday.

The wild conditions are in stark contrast to scorching temperatures in Western Australia, where parts of the state are under a high fire danger warning.

Two dozen people were rescued from dangerous flooding in the 24 hours to Tuesday morning, with warnings for the Campaspe and Goulburn rivers in central Victoria.

Residents who stayed overnight in Seymour, Yea and Rochester, it was too late to evacuate on Tuesday.

A band of heavy rain, fueled by tropical moisture, produced record-breaking rain, including in Heathcote, where 154mm of rain fell in the 24 hours to 9am on Monday morning.

It was the heaviest rain in January and the second wettest day since city records began in 1882.

Bendigo broke its daily rainfall record with 91.8mm in the 24 hours to 9am on Monday.

Flooding in some areas could continue for the next five days, with levels in Seymour expected to be higher than 1993 levels.

Weather Zone meteorologist Stephen King told Daily Mail Australia central Victoria that there will not be much rain in the coming days.

'The conditions look quite good. In New South Wales, the rain has largely cleared, leaving skies only partly cloudy,” he said.

“Northeast NSW will see thunderstorms with some activity in the south-east and Canberra.”

That wet weather will hit Canberra on Tuesday before skies partly clear on Wednesday.

The outlook for Sydney is also bleak, with showers on Tuesday turning to cloudy weather on Wednesday.

The rest of the week is expected to be wet, with showers from Thursday to Monday.

Mr King said clear conditions would continue in central Victoria until Friday.

“The next few days look nice and sunny,” he said.

“There may be a few afternoon thunderstorms on Friday, but nothing like what we've seen over the past few days.”

Melbourne will be cloudy on Tuesday, with skies remaining gray through Thursday.

The city is expected to have one day of sunshine on Friday before showers pass on Saturday.

Rainfall in Brisbane will continue until the end of the week, with wet conditions bringing temperatures ranging from 20ºC to 30ºC.

Perth can expect windy conditions on Wednesday, with winds turning southerly to south-westerly at speeds of 30 to 40 km/h, reaching 50 km/h near the coast by early afternoon.

High temperatures in the Western Australian capital will remain in the low to mid 30s Celsius for the rest of the week, with Friday set to be the warmest day at 35 degrees Celsius.

Meanwhile, several districts in the state will experience extreme heatwave and high fire hazard.

Mr King said the worst of the heatwave would extend from the Pilbara to the Goldfields.

“Unfortunately, the hot air will remain there for the next week, with temperatures well into the 40s Celsius,” he said.

“It will remain that way at least until this time next week.”

The heatwave is expected to reach Perth on Thursday or Friday.

It will remain partly cloudy over Adelaide on Tuesday and Wednesday, before clearing to sunny skies on Thursday.

Hobart will see similar weather with gray skies on Tuesday and Wednesday, ahead of a sunny Thursday.

Darwin is still in the middle of the wet season, with rain showers and possible storms forecast until next week.