Heatwave records continue to tumble across eastern Australia, with many Victorians sweltering through their hottest days on record.

The cities of Albury and Wodonga, which span the Murray River border between New South Wales and Victoria, recorded their hottest ever days Wednesday, with the mercury topping 45.3C.

The Bureau of Meteorology confirmed the statistics on Thursday, warning there is more hot weather on the way.

The warning comes as BoM predicted the heatwave to peak in New South Wales on Friday.

“The extreme heatwave across northern Victoria produced a few records yesterday: 45.3 degrees in Albury-Wodonga was its hottest day on record, that record spanning over 30 years,” senior meteorologist Rod Dickson said.

Hunters Hill, just east of Albury, also had its hottest day on record with a top of 38.3 degrees.”

Other centres made the record books, with Mangalore, two hours north of Melbourne, reaching 44.8C, its hottest ever January day.

The northern township of Yarrawonga’s maximum of 45.7C equalled its hottest recorded day.

“Broadly speaking across the north [of Victoria] yesterday temperatures ranged between 45 and 46 degrees, so some pretty extreme heat,” Mr Dickson said.

Overnight brought only slight relief, as temperatures dipped to about 27C.

The heat wasn’t forecast to be quite as extreme on Thursday due to some patchy cloud, with forecasts of between 42C to 44C and a maximum of 45C at Mildura.

Gusty afternoon winds and the possibility of dry lightning has prompted a severe fire danger warning for the Mallee, Wimmera and northern country.

Melbourne was expected to reach 37C in the afternoon with an evening change dropping the temperature but humidity remaining, Mr Dickson said.

A southerly change is due to reach Melbourne late on Friday morning and extend through to northern Victoria later in the day.

The heatwave over Australia is pictured up to Friday. Source: BoM

In NSW, maximum temperatures in most of the state were expected to stay above 41 degrees until Friday, something not seen in 80 years.

Penrith is forecast to reach 45 degrees on Friday, with the city to hit 34. Temperatures of up to 47 degrees are expected to continue inland.

Meanwhile, 16 people presented at South Australian emergency departments with heat-related conditions in the 24 hours to Wednesday afternoon. Seven people were admitted for further treatment.

More admissions were expected, with authorities warning health issues were more likely after several days of sustained hot weather.

White Cliffs in NSW topped 48.2 degrees on Wednesday, its hottest ever, along with Wilcannia on 47.9 degrees.

Tuesday was even warmer in South Australia, when the small town of Tarcoola hit a scorching 49 degrees. Port August reached 48.9.

-with AAP