Melbourne is set to swelter in 44-degree day heat today, which could be the hottest day since Black Saturday.

Swan Hill and Mildura are expected to reach 47C, which will break their temperature record, which sits at 44C.

The fire danger rating is set from very high to extreme across all regions.

“We saw more than 40 fires on Wednesday, and in some respects that was a taste of what will be coming on Friday,” Emergency management commissioner Andrew Crisp said on Thursday.

“We cannot afford to be complacent in any part of the state tomorrow. It will be a tough and challenging day for the state. We’re doing everything we can, what are you doing?”

A cool change is expected to hit the state at around Midnight tonight, with Saturday set to be a cool 20 degrees.