A heatwave covering around two thirds of the country is underway and appears likely to last until the middle of next week.

Parts of every single state and territory will be affected, while the entirety of three states and one territory – South Australia, Victoria, Tasmania and the ACT – will be under the influence of a low to severe intensity heatwave from Saturday through to Monday.

Just how hot will it be?

For any location in Australia, the BoM defines a heatwave as a three-day stretch when the maximum and minimum temperatures are "unusually hot" compared to the local climate and past weather.

So you don't need record-breaking temperatures for a heatwave, but you do have to see a run of temperatures which are significantly above average. For example:

• Melbourne is heading for maximums of 37°C, 37°C and 38°C from Sunday through to Tuesday, with minimums of 20°C, 22°C, and 25°C.
• Melbourne’s average February maximum is 25.8°C and average February minimum is 14.7°C.
• That’s three days when maximums will be 11 to 13 degrees above average with minimums that are 5 to 10 degrees warmer than average.

So even though Melbourne won't get within coo-ee of its all-time February (and annual) high temp of 46.4°C (set in 2009), it will still be experiencing a heatwave. Indeed, the city is heading for its hottest 3-day spell in 11 years.

Image: Daily Forecast on the Weatherzone app for Adelaide, SA, as at 10:47am ACDT on January 31, 2025.

It’s a similar story in Adelaide, where the record temp of 46.6°C (set in January 2019) won’t be threatened. But after maximums in the high 30s over four days and minimums in the 20s for several nights, locals will know they’ve endured the most sustained hot spell of the 2024/25 summer to date. 

Image: Heatwave map for Australia from Sunday, February 2, through to Tuesday, February 4.

Meanwhile the Apple Isle looks decidedly orange on the heatwave map, with Hobart’s hottest day looking to be Tuesday, with a maximum of 34°C.

The northeast corner of Tasmania often cops more prolonged heat in these events, and Launceston is heading for tops of 34°C, 35°C and 33°C from Sunday through to Tuesday. These temperatures will be around 10 degrees above the average February maximum.

Why the prolonged heat across the southeast?

Extreme heat has been building up over the centre of the continent for more than a week now, with little change in the overall weather pattern.

As the high pressure system centred over the Great Australian Bight shifts slowly east towards the Tasman over the weekend and into the new week, northerlies circulating around the high will carry baking hot air southwards.

Image: Synoptic chart for Monday, February 3. Note the orange arrow indicating hot air being dragged down all the way to Tasmania.

For the east coast, there will be just enough of a cooling easterly influence to stop coastal locations like Sydney hitting temps much higher than 30°C.

But it will be a different story for mainland areas south or west of the Great Dividing Range – with multiple days of 40–degree weather across western NSW and northwestern Victoria.