An emergency warning has been issued for the towns of Glenisla Crossing and Glenisla, in western Victoria, as a large blaze threatens rural homesteads.

The out-of-control fire was fanned by strong winds overnight, but the situation eased briefly, before flaring up again just after sunrise.

The large, fast-moving fire is travelling in a north-westerly direction and is expected to hit the towns in the next few hours.

The fire has now burned through more than 31,000 hectares.

Incident controller Stuart Broad says fire behaviour had slowed under lighter winds this morning.

"We intend to monitor this one very, very closely today," he said.

"We are hoping that by lunchtime that north-easterly wind will have abated.

But Mr Broad says they were expecting conditions to deteriorate.

"It's a bit like a sleeping dragon. It actually dies down a little bit. And it'll die down and be reasonably quiet now for the next few hours," he said.

"As soon as the sun comes up and the humidity starts to drop again we will see significant activity pop up again."