Heat reprieve for some but others set to swelter again

Heatwave conditions are set to continue across inland regions of south-east Australia, as coastal cities enjoy a brief reprieve after record-breaking temperatures.

Residents living at Renmark, in South Australia's Riverland region, experienced their hottest day on record on Tuesday, with temperatures reaching 49.6C, while Victoria smashed its own heat record as Walpeup in the state's north hit 48.9C.

Cooler conditions are expected for much of Victoria on Wednesday, although the heatwave gripping inland regional areas is far from over.

Senior meteorologist Dean Narramore told AAP that hot air was pushing into north-west NSW and Queensland, bringing another day of extreme fire danger and scorching conditions.

Mildura, in Victoria's Mallee region, won't see any relief from the heat, with the regional city set to remain in the 40Cs until at least Sunday.

"We are expecting another four days of above 40 degree temperatures and overnight temperatures in the mid-20s in the north of the state," Emergency Management Commissioner Tim Wiebusch said.

An extreme heatwave warning remains in place for several regions on Wednesday, including the Mallee, Wimmera, Northern Country, East Gippsland, West and South Gippsland and North Central regions.

Victorian Chief Health Officer Caroline McElnay said severe heatwave conditions are dangerous for many vulnerable people in the community.

"It can cause potentially fatal health problems such as heat exhaustion and heat stroke, but it can also trigger events like heart attacks or stroke," Dr McElnay told reporters on Tuesday.

"Please take steps to protect yourself and others by keeping cool. Stay hydrated. Plan ahead to avoid the heat and check in with others."

Melburnians will experience a top of 24C on Wednesday, while residents living in Adelaide will see a high of 30C.

It's a far cry from conditions experienced just 24 hours earlier, with Melbourne recording a top of 42C, a few degrees short of its record high of 46.4C set on February 7, 2009.

Mildura hit a top of 48.6C, marking its hottest day on record, while the nearby towns of Hopetoun and Ouyen climbed to a scorching 48.9C.

Records were broken on Monday in Adelaide where the temperature reached 44.7C, exceeding the city's previous Australia Day heat record set in 2006.

Ceduna, northwest of the SA capital, climbed to 49C, surpassing its previous record, while NSW town Dubbo reached 46.1C to record its hottest January day.