Play at the Australian Open tennis in Melbourne was suspended on Tuesday afternoon as part of the tournament's official Extreme Heat Policy.

Players were called off outside courts when temperatures topped 36°C, and while anyone who knows Melbourne summer weather would understand that 36°C is hardly extreme, it's hot enough to stop play under the AO Policy, which you can read here.

A heat policy was first implemented in the 1998 Australian Open. Since then, it has been tweaked to allow for factors beyond just the air temperature – such as humidity, wind speed and radiant heat which can cause courtside spaces to become much hotter than the air outside the tennis complex.

Presumably that's why temperatures of 36°C were recorded at Melbourne Park at 2 pm when temps were a couple of degrees cooler at Melbourne's official weather station at Olympic Park just a stone's throw away.

The AO Heat Stress Scale has reached 5 and play will be suspended on the outside courts. This means play continues until the end of an even number of games or the completion of a tie break. No new matches will be called to court. Play on outdoor practice courts is also suspended.

— #AusOpen (@AustralianOpen) January 17, 2023

Meanwhile as we're writing this story around 4:30 pm (AEDT), temps keep rising in Melbourne. The mercury touched 37.2°C at 4:40 pm and may yet peak higher as hot northerly winds continue to buffet the city.

Further west in Victoria it has been a scorcher, with a statewide high to 4:20 pm of 42.3°C at Walpeup in the Mallee region – one of numerous 40+ readings in western districts.

But a cooler change is on its way overnight and into Wednesday, and with it, storms are brewing.

A severe thunderstorm warning was issued just before 4 pm on Tuesday afternoon for parts of Victoria's Wimmera, Mallee and South West forecast districts, as the atmosphere becomes unstable with a trough and approaching cold front meeting those hot northerly winds.

There's a chance of a squall line developing as the storms sweep across the state overnight and for those of you who love to learn about the weather, earlier today we wrote a story explaining what squall lines are.

If you look closely at the image above, you'll note that southeastern SA is much cooler than Vic with winds having swung around to the southwest. Adelaide reached 36.6°C at 10:48 am today before the change.

The whole of Victoria can expect much cooler maximums tomorrow, with no location likely to see 30 degrees, and Melbourne's maximums likely to stay under 30°C for at least the next seven days – making for perfect tennis weather.