The weather bureau is forecasting possible snow in the Victorian alps.

Temperatures reached the mid-40s in northern parts of the state during last week's heatwave, as fire authorities responded to hundreds of bushfires.

But it has cooled significantly since then, reaching just 3.4C at Mount Hotham today.

The bureau's senior forecaster, Richard Carlyon, says it is expected to get colder by Wednesday.

"Quite a cool blast for summer, it might only be an 18 degree day [in Melbourne]," he said.

"We're forecasting some snow over the Alpine peaks. Quite a cool blast there.

"That really puts a hold on the warm weather, so it will take quite some time to recover from that."

He says the weather should start to warm up in about a week or so with temperatures creeping up to the 30 degree mark.