"Parts of central Western Australia, South Australia, Victoria, New South Wales and Tasmania are forecast to experience a severe heatwave until Thursday, with the hot weather contracting to New South Wales and Queensland on Friday and Saturday...

"The hottest spot in NSW will be Menindee, near Broken Hill, with forecast temperatures of 45C on Monday rising to 47C on Thursday, and Friday expected to contribute to more fish deaths.

"As many as 1m fish are believed to have died in two mass fish kills in the Menindee Lakes since December.

"The heatwave is caused by a strong high-pressure system that has dragged hot air from the Pilbara in Western Australia, where temperatures in Marble Bar have been above 40C since mid-December, said Ashleigh Langey from the Bureau of Meteorology...

"hot weather records could be broken in northern Victoria, with temperatures of 46C forecast for Mildura on Tuesday and Mildura, Swan Hill and Echuca on Wednesday. Albury-Wodonga, Shepparton and Wangaratta are also forecast to be very hot.

"The hottest temperature ever recorded in Mildura is 46.9C.

"“If we get to 47C in the next couple of days then we will be breaking not just January records but all-time hot weather records as well,” BoM senior forecaster Michael Efron said.