It was a cold morning across southeastern Australia as you'd expect after the passage of an autumn cold front, with subzero readings in three states.

Australia's highest weather station near the top of the Kosciuszko chairlift at Thredbo recorded 25 consecutive hours of subzero temperatures from 7 am Tuesday to 8 am Wednesday, as well as Australia's lowest minimum on Wednesday morning.

Subzero readings occurred in three states (including the ACT), with the lowest being:

• NSW: Thredbo Top Station –2.7 °C
• VIC: Mt Hotham –1.9°C
• ACT: Mt Ginini –1.8°C

No subzero temps were recorded in Tasmania, although a couple of locations came very close including Fingal in the state's northeast.

But the autumn chill wasn't just restricted to the mountains or the southern states, with cool overnight temps spreading northwards as far as Queensland and northern SA.

It's all thanks to the cool Southern Ocean airmass circulating around the strong high pressure system centred southwest of Perth, which is illustrated on the chart above.

Numerous locations in inland southern Queensland had single-digit minimum temps and while that is nothing too dramatic for April, the apparent or "feels like" temps would have made life uncomfortable for anyone with an early start.

For example, Toowoomba's official minimum was 7.7°C which was the coldest night of the year to date by almost 7 degrees, but the "feels like" temp around the same time with moderate southwesterly winds blowing was just 3°C, making it seem all the colder. 

Cool minimums can be expected to continue throughout the working week in most of the places mentioned, as that stubborn high pressure system is not going anywhere in a hurry.