Victoria, NSW to cop more extreme heat

Melbourne and Sydney are expected to cop more extreme heat over coming days, with temperatures across Australia's southeast predicted to reach into the low 40s.

The Bureau of Meteorology says temperatures in Melbourne, Sydney, Canberra and Adelaide are forecast to range from the high 30s and into the low 40s from Wednesday, after a relatively cool start to the week.

"Tomorrow we'll start to see the heat build over South Australia and western Victoria. On Thursday, we'll see that heat move into other parts of Victoria and western NSW and Tasmania as well," senior meteorologist Jonathon How said on Tuesday.

"On Friday, we'll see that heat move into the rest of NSW and the ACT as well, and thankfully there will be a little bit of relief over southern parts of the country with a cold front.

"However, unfortunately the heat will linger over central and eastern parts of NSW well into the weekend."

A cold front is expected to bring relief to coastal SA, Victoria and parts of Tasmania from Friday night but conditions will remain fairly dry.