With two large bushfires burning in Victoria's east, crews have also been kept busy by smaller fires across the state.

In the alpine region, about 250 firefighters continued to tackle the Harrietville fire as Wednesday's dry, windy heat fuelled the blaze, creating huge smoke plumes, the CFA said.

The fire is yet to be contained and could cross the Great Alpine Road - which remains closed near Harrietville - about 12 kilometres south of the town, moving west, it said.

Grass fires also broke out near the western towns of Ballarat and Warrnambool, but neither had threatened properties, and both were declared safe within about an hour, a CFA spokeswoman said.

"Small things have been happening, but they've all been controlled fairly quickly," she said.

"The weather will continue to get hotter, though, so we'll have to wait and see what happens overnight."

Daily maximum temperatures are tipped to reach the mid-to-high 30s in much of the state until Sunday.

Most of Victoria will be subject to a total fire ban on Thursday, with many areas experiencing a severe fire danger rating, after bans in four fire districts on Wednesday.

The total fire ban is in effect for the northern, northeast, East Gippsland, West and South Gippsland, central and north central districts for Thursday.

About 140 firefighters have been deployed at the Aberfeldy fire in Gippsland, where they've built a 300km control line and have been conducting extensive back-burning.

At Harrietville, back-burns have been completed south of the town to offer greater protection, with another to Mount Hotham's northwest to limit the potential spread of the fire.

The Department of Health has warned Harrietville residents to boil their drinking water as sediment pushed into the river has contaminated the town's supply.

The Harrietville fire has burned about 7000 hectares since it started on January 21, while the fire in Gippsland has burned about 75,000 hectares, killed a man and destroyed 21 homes.