Following a polar blast this week, temperatures across south-east states will soar as much as 12 degrees Celsius above average this weekend.
The rapid warming is due to an in-feed of air from Australia's north-west "heat engine" which has already brought dozens of temperature records to Western Australia this week.
The first summer outlook has also now arrived, and in a repeat of the spring forecast, weather modelling is indicating the potential for record heat.
Frigid air from Antarctica dropped temperatures as much as 10C below average this week over south-east Australia, and snow fell close to sea level in Tasmania.
The warmest air swept through WA on Thursday and Friday, it will reach western South Australia on Saturday, followed by the east on Sunday.
For several capitals, maximums should be the highest in years for early spring:.
Sydney city is predicted to bathe in a summery 28C on Saturday and Sunday, but away from a sea breeze, western suburbs are tipped to peak from 30C to 34C.
Much of the south-east inland is also heading into the low-to-mid 30s this weekend, and again for some towns and cities, like Mildura and Griffith, maximums should be the highest in years for September.
Just as quickly as the heat arrives, it will be flushed away by another polar air mass sweeping in off the Southern Ocean, dropping temperatures 10C to 15C in 24 hours.
October and November are also likely to be dominated by above-normal temperatures, potentially raising the season's average above the hot springs from 2024 and 2020.