A warm week by winter standards is in store for the most populated corner of the country, with maximum temperatures trending around two to five degrees above the June average in the southeastern capitals, and most places in between.

Why are temperatures so mild this week?

A slow-moving high pressure system is centred over the Tasman Sea between Australia and New Zealand, and will be more or less parked there for the remainder of the working week.

While a cold front is lashing the southwest of Western Australia this Tuesday, the Tasman high is forcing cold fronts down into the Great Australian Bight and further south, steering them away from southeastern Australia.

Burst of cool air for southwest Western Australia

It's actually a bitterly cold winter morning in large parts of southern WA today. For example, the apparent or "feels like" temperature was just 1.7°C at 9 am (AWST) at Esperance Airport in the state's South East Coastal forecast district.

Meanwhile Perth is heading for an expected high of just 17°C this Tuesday. Of the capitals, only Canberra (15°C) is forecast to be cooler. But even Canberra could hit the high teens later this week.

Let’s switch from west to east and see what to expect in the southeastern capital cities this week.

Adelaide

The mercury should reach around 20°C in Adelaide this Tuesday. Maximums should then dip slightly into the high teens on Wednesday and Thursday before another warm surge brings a top as high as 23°C on Friday. Adelaide’s average June maximum is 15.8°C. 

Melbourne

It’s not often that Melbourne sees a 20-degree day in June. While there was one in both 2023 (20.1°C on June 5) and 2025 (20.4°C on June 2), you have to go all the way back to 2006 to find the previous one.

But 20 degrees is on the cards for Friday after a run of unseasonably mild maximums in the high teens midweek – even though gusty winds at times will make things feel much cooler than the still-air temperature. Melbourne’s average June maximum is 14.1°C.

Image: Daily forecast for Melbourne, Vic, on the Weatherzone app.

Hobart

Unlike Melbourne and Adelaide where the week’s temperature spike should occur on Friday, Wednesday looks like being Hobart’s warmest day, with a top of 18°C. The average June maximum is just 12.1°C, and no day this week is expected to peak lower than 15°C.

Canberra

After a string of frosty mornings over the long weekend (the lowest was -2.4°C on Monday morning), Canberra minimums won’t come close to freezing from Wednesday through the rest of the week.

Maximums will range from around 15°C to 17°C all week. The average June maximum in the national capital is 13.2°C.

Sydney

Sydney had already hit 20.2°C by midday this Tuesday, and maximums should reach the low 20s all week. Sydney’s average June maximum is 17°C.

And since we’ve mentioned six of Australia’s eight capital cities so far, we shouldn’t forget Brisbane and Darwin, both of which can expect maximum temperatures only a degree or so above the monthly average for June all week.