AUTHORITIES are urging Victorians to recheck their bushfire plans ahead of a forecast scorcher on Thursday.

Severe fire danger conditions, the third highest rating, are being predicted in the state's central region, including Melbourne and Geelong, north central and southwest districts.

Melbourne is expected to reach 39C.

"We're certainly bracing for a potentially bad day on Thursday," a CFA spokesman said.

Acting Victorian chief health officer Michael Ackland has issued a heat health alert for the day, reminding people at risk to take precautions.

He's urging those aged over 65, pregnant women and people with existing illnesses to keep cool, drink plenty of water and stay out of the sun.

It is also important for people to check on their elderly neighbours or relatives, Mr Ackland says.