Thursday has been the warmest September day on record at key locations in Australia's snowfields, with the two largest ski resorts in New South Wales both shattering the old monthly record by a degree or more.

Perisher reached 19.3°C just before midday. The old September record was 18.0°C in data going back to 1976.

Thredbo Top Station (Australia's highest weather station at 1957 m) reached 16.0°C at 11:15 am. The old September record was 15.0°C in data going back to 1966.

Why was it so warm in the snowfields this Thursday?

When it's warm in both Melbourne and Canberra, it's usually warm in the Australian Alps, which lie in between those two cities.

And it has indeed been warm for September in both Melbourne and Canberra today, with the mercury in Canberra coming close to 25°C while Melbourne peaked around 26°C.

But these were hardly extreme temperatures for September. Indeed, both cities have already had warmer days this month. So why did the snowfields break records today?

"It was due to a layer of air around six thousand feet [approximately 1800 m] in the atmosphere," explains Weatherzone Director of Meteorology Duncan Tippins.

"Temperatures at lower elevations were closer to normal for this time of year, but places like Thredbo and Perisher felt the effect of the warm layer."

The effect of the warm air layer at higher elevations was well illustrated by today's maximum of 17.8°C in the tiny town of Cabramurra, about an hour north of Perisher.

Perisher is around 300 metres higher than Cabramurra, which means Perisher would usually be considerably cooler during the afternoon, as temperatures drops as you ascend in altitude. But due to that warm air layer, Perisher's maximum today was 1.5 degrees warmer than Cabramurra's.

More warm weather, then Sunday snowfalls

Snow is on the forecast for Sunday in the mountains as a burst of cold air pushes in from the southeast.

Before then, the maximums on Friday and even Saturday could come within a degree or so of Thursday's temperatures, although it doesn't appear likely at this stage that further September heat records will tumble.

Image: Ski patrol with not a lot of people or terrain to patrol at Perisher on Thursday, September 24, 2026. Source: Steve Smith.