The Bureau of Meteorology has revised Melbourne's forecast to 27 degrees after a high of 32.6 at 9.17am.

The prediction is a relief for city workers after temperatures up to 38 degrees yesterday.

The city had an overnight low of 28.1 at 4.47am - only 2.4 degrees cooler than the warmest night ever recorded on February 1, 1902.

Melbourne's forecast is in the low- to mid-20s for the remainder of the week, before a return to the mid-30s on Monday.

Forecasters are still expecting a sweltering conditions today in the north of the state, with Swan Hill heading towards 45 degrees.

The city had topped the 40-degree mark by 11.30am, while others including Mildura (39.1) and East Sale (39) were also heating up.

Victoria's highest temperature yesterday was recorded at Ouyen, in the state's north, where the mercury reached 42 degrees.

Other parts of the state, particularly in the Mallee and Wimmera districts, recorded highs in the low 40s.

James Taylor, from the Bureau of Meteorology, said many places north of the Great Dividing Range would hit the low 40s today.

Ambulance Victoria has warned people to be aware of the hot weather after two heat-stress incidents this week.

Operations manager Paul Holman said parents should avoid exposing children to the heat of the day and in no circumstances leave a child unattended in a car.

Joggers and cyclists were warned to delay exercising until evening and people were asked to check on elderly neighbours to confirm their welfare.

"During extreme conditions, we really need relatives, neighbours and friends to take care of those at risk,'' Mr Holman said.

A total fire ban is still current for the state.

A Country Fire Authority spokeswoman urged people to observe the ban after an unattended campfire burnt eight hectares near Clunes yesterday.

A list of approved activities during a fire ban is available at the CFA website at www.cfa.vic.gov.au.

This week's heat came as a rude shock to many after the cool start to summer, but Mr Taylor said temperatures were not unusual.

"We have seen a cool start to summer, there's no doubt about that and a lot of locations were around a degree below average for December," he said.

"This hot air mass certainly feels out of the ordinary this year, but it's certainly not out of the ordinary in general for Victorian summers."