Searing heat and thunderstorms are set to sweep the state later this week, with warnings of a return to temperatures above 40 degrees putting fire-ravaged areas of Victoria back on high alert.

Most of East Gippsland is forecast to hit temperatures in the high 30s on Friday, while Albury is set to experience two days over 40 degrees on Friday and Saturday. Melbourne won't escape the sweltering heat, with 37 degrees forecast for Thursday and a humid top of 41 expected on Friday.

Bushfire damage is seen near Tambo Crossing beside the Great Alpine road in the Victorian high country. The route was reopened on Monday. Credit:AAP

"Unstable" storms and a cool change on Saturday will bring thunder, lightning and stronger south-westerly winds, according the Bureau of Meteorology.

Victoria's fire authorities are now working to reinforce containment lines, with 10 fires still burning across the state, eight of those in East Gippsland.