It's still only early autumn so you expect some summery heat to be sticking around, and the whole of southeastern Australia is in for a prolonged warm spell with temperatures set to peak this coming weekend. 

• For Adelaide, the hot weather started on Tuesday with a top of 34.1°C and continues this Wednesday with a top of 34°C expected, followed by 33°C on Thursday, 36°C on Friday, 39°C on Saturday, 36°C on Sunday, 36°C on Monday, and 32°C next Tuesday.
• Melbourne will be the next capital to feel the heat, rising rapidly from the mid-20s in the working week to a scorching 38°C on Saturday, with top temps remaining in the 30s for at least a couple of days.
• Canberra will also see a run of at least five days with maximums of 30°C or higher, while the east coast will be spared the hottest weather, with temps only nudging 30°C from Brisbane southwards to Sydney, although western Sydney will likely reach the mid-30s.

The culprit for this warm autumn spell is what's known as a "blocking high" – a strong high pressure system which forms further south than usual. Typically, blocking highs are slow-moving, which allows heat to build up as the progression of weather systems across southern Australia is blocked.

The Saturday chart above showing the high centred over the Tasman Sea is a classic example, with hot northerly winds circulating anticlockwise around the high.

The buildup of heat enabled by the blocking high will create low-to-severe intensity heatwave conditions in at least four states plus the ACT, with max temps reaching close to 40°C for up to a week in northwestern Victoria and far western New South Wales. 

Be sure to check our warnings page for the latest info on heatwaves and other severe weather.