Temperatures on Saturday and Sunday are set to nudge 40 degrees in Melbourne, and rising even higher in some regional areas.

The capital will reach 30 degrees today, before a sharp peak tomorrow.

Saturday is forecast to top out at 38 degrees, followed by 37 degrees on Sunday.

Despite the fire threat in the Gippsland and Grampians areas being downgraded, fire authorities will also be watchful for any strong winds or changing conditions.

A cool change on Monday will also bring plenty of rain.

Further north in New South Wales, Sydney will enjoy a balmy Saturday, with the Bureau of Meteorology forecasting a top of 29.

But that will spike into the mid-30s on Sunday and Monday, before a cool change drops temperatures to the mid-20s for the rest of next week.

Brisbane will see consistent weekend temperatures of around 30 degrees at most, with the chance of rain on Saturday.

Adelaide will be a warm 36 on Saturday with plenty of cloud cover, cooling slightly to 33 on Sunday.

The weekend will be sunny in Perth, with a top of 32 degrees on Sunday, while Darwin will be stormy, with tops of 33 degrees both days.

A mild 28 degrees in Hobart on Saturday will call to 22 degrees on Sunday, with a chance of rain.

Canberra meanwhile faces a hot one, with a top of 34 degrees on Saturday and 35 on Sunday, followed by a possible Monday storm.