Fire threat remains in Vic Grampians

A massive bushfire in Victoria's Grampians region will continue to pose a threat to nearby communities with conditions expected to worsen overnight.

The 1500 hectare Northern Grampians complex, which is the product of two out-of-control bushfires that merged, forced authorities to issue emergency warnings for surrounding towns on Thursday and urge visitors to leave the popular camping area.

The fire is burning in difficult-to-access terrain, and could pose a major threat to life on property with very hot temperatures a gusty south westerly change predicted for Friday.

Fire Services Commissioner Craig Lapsley said the fire had increased in intensity and would likely burn out of control until Friday.

"That will be a going fire on Friday when the temperatures are high and the wind speeds from the southwest will be at their height," he told reporters.

"That's a fire that has significant potential."

An emergency warning remained in place for the towns of Roses Gap, Wartook, Heathvale, Laharum and Zumsteins was downgraded on Thursday night.

The Wartook Valley is the major entrance to the park on the northwest side.

A telephone alert was sent to visitors in the park telling them to leave.

Farmers were advised to consider moving their stock to safer areas with reduced fuel loads, water and food.

Lightning sparked a number of fires at the north and south ends of the park overnight Wednesday.

AAP pbc/wf