Rain, lightning a mixed blessing for Vic

Firefighters battling the Moyston blaze in Victoria's west have been given some respite by storms that brought rain to the region - but also lightning that has triggered more fires.

Conditions are expected to ease further with a cool change on Saturday evening, and the Bureau of Meteorology has issued a severe thunder storm warning for the state's western half.

Heavy winds, hail and rains could lead to flash flooding, the bureau has warned.

Horsham Deputy Incident Controller Graham Parkes said the rain so far had been patchy, and a mixed blessing.

"The storm cells are coming from South Australia," he told AAP on Saturday.

"But with the storms come lightning and now we're responding to eight or so new fires in the district."

Heavy rain and high winds hit Ararat - where there is a relief centre for the Moyston fire - about 3.20pm on Saturday.

Heavy rain fell for about 10 minutes, at first with specks of small hail.

Rolling thunder and frequent flashes of lightning are still occurring.

The Moyston fire destroyed a home on Friday and still poses a threat to the nearby town of Maroona, and there is an active warning for residents to evacuate.

The head of the fire is contained, but there are concerns about breakouts given the changing weather conditions and wind directions.

The Country Fire Authority set up a relief centre at the Horsham and Lake Bolac, but are expected to close Lake Bolac late Saturday afternoon.

The Moyston fire has destroyed almost 5000ha since Friday, including one home, four sheds and an unknown number of livestock.

Firefighters used 80 vehicles and 11 aircraft to battle the blaze on Friday.

More than 250 CFA staff worked around the clock on Saturday.