It's still only the third week of autumn so you expect plenty of warm days persisting in southern Australia, but pretty much all of Tassie had an extra warm one on Thursday.

Hobart reached a top of 29.2°C, which was exactly nine degrees above the average March maximum of 20.2°C.

Statewide, maximums in the mid-to-high twenties were prevalent, including Dennes Point (25.7°C), Cape Bruny (27.9°C) and Smithton (25.8°C), all of which had their hottest March day in three years.

The remarkable thing about today's warmth is that it occurred under high cloud which prevented the full force of the sun warming our southernmost state yet further.

As you can see on the afternoon satellite image below, a band of cloud was crossing the state, and light rain was recorded in all forecasts districts except the Upper Derwent Valley.

Despite the cloud, temps still rose to near 30 in many places because of the strong northerly component to the winds, dragging warm air all the way south from the NSW/Qld border region. You can see that illustrated in simple terms via the orange arrow on today's synoptic chart.

The northerly winds explain why much of southern Victoria also had a warm afternoon, with the temp reaching 30.5°C at Melbourne Airport.

Cooler temps will return to Tasmania and southern Vic tomorrow in the wake of a weak cold front. Hobart is heading for a top of just 18°C.