Maximum temperatures will fluctuate quite dramatically across most of southern Australia over the weekend and into the new week, as the spring 'see-saw' takes full effect.

Let's take a look at forecasts for the southern capitals over the coming seven days, before examining the reasons behind the contrasting temperatures.

Melbourne maximums (from this Friday, September 11 through to Thursday, September 17)

16°C, 22°C, 23°C, 20°C, 14°C, 14°C, 15°C

It has been cool all week in Melbourne. Wednesday's high of 13.8°C was the chilliest maximum since August 11. September's average maximum is 17.3°C. Expect another chilly outbreak next week.

Adelaide maximums (from this Friday, September 11 through to Thursday, September 17) 

21°C, 24°C, 22°C, 18°C, 17°C, 18°C, 20°C

Adelaide's temperatures won't bounce around as much as some other capitals, but there will still be a noticeable cooling next week after some weekend warmth. September's average maximum is 18.5°C.

Canberra maximums (from this Friday, September 11 through to Thursday, September 17)

21°C, 21°C, 22°C, 23°C, 19°C, 16°C, 20°C

While Canberra's maximums will dip midweek after a warm spell, minimum temperatures are always a big part of the Canberra weather story too, and after sub-zero minimums the last two nights, frosty mornings will likely return by the end of next week after a few slightly warmer nights.

For those who enjoy interesting meteorological facts, Canberra has recorded sub-zero minimums in all months except January and February.

Image: 2-metre temperatures and 10-metre winds across Australia at 4 pm (AEST) on Wednesday, September 16, 2026, showing the contrasting temperatures between the east and west of southern Australia.

Perth maximums (from this Friday, September 11 through to Thursday, September 17)

25°C, 21°C, 21°C, 24°C, 27°C, 30°C, 27°C

In the case of Perth, it's not how much the temperature will dip, but how much it will rise after a brief cool spell with a weakening cold front over the weekend. Next Wednesday could be the city's first 30-degree day since April. Perth's average September maximum is 20.7°C. 

Sydney maximums (from this Friday, September 11 through to Thursday, September 17)

20°C, 21°C, 23°C, 27°C, 25°C, 18°C, 20°C.

As the harbour city warms up next week, it won't get nearly as hot as the 32.1°C last Saturday, which was the highest reading in the first week of September in data going back to 1859. But there should still be a temperature difference approaching 10 degrees between next Monday and Wednesday's maximums.

Sydney's average September high is 20.2°C.

Hobart maximums (from this Friday, September 11 through to Thursday, September 17)

18°C, 19°C, 22°C, 21°C, 13°C, 15°C, 16°C

After a warm spell on Sunday and Monday, Hobart residents will be reminded that they live in Australia's southernmost capital, with a wintry burst on Tuesday. The average September maximum is 15.2°C.

Cold front pushes the see-saw

A cold front will push into southwest WA on Friday night, delivering only a few showers as it will be a weakening system when it arrives.

That front will slide southwards as it crosses the Great Australian Bight, but a second front should make a direct hit on Tasmania and clip the southern mainland around Tuesday next week. That's the system that will cause a big temperature drop in some parts of southeastern Australia.

The general progression of these systems from west to east will generate showers along Australia's southern coastline and nearby ranges, but no big rainfall totals are expected on the mainland.

Western Tasmania tends to get the most rainfall from this kind of spring weather pattern, and that will be the case into the new week.

Image: Predicted rainfall accumulation across SE Australia up until 10 pm (AEST) on Thursday, September 17, 2026, according to the ECMWF model. Source: Weatherzone.