The Bureau of Meteorology tips temperatures will reach up to 42 degrees in parts of the region on Thursday, and 45 on Friday.

The mercury had already soared past 30 degrees in many places by 9am on Thursday. By noon, it had pushed past 37 degrees. 

The fire authority has declared a total fire ban for Thursday and Friday, and the Department of Health and Human Services has issued heat health alerts for the Mallee and Wimmera regions for Friday.

Heat health alerts are also in place for the Mallee on Saturday and Sunday.

The authority’s district 17 operations manager Dale Russell said an incident control centre in Horsham was set up ready to respond to any major incidents.

“We've got a number of people who support the control centre when they require more vehicles, equipment or personnel,” he said.

“The initial response to any incident is by volunteers, but if they cannot control it and it looks like becoming a major event, it then moves under the command of the incident control centre.

“Any public messaging and warnings would then come from the centre.”

Mr Russell said people needed to stay alert to the conditions, and rethink any outdoor activities.

“We encourage people to be aware of the situation, where they are and what’s happening around them,” he said.

“Another important point is don’t rely on one source of information, whether that be an app, radio or the internet.

“Our biggest message is for people to defer any work they had planned to do outside, so they not only stay out of the heat for their own wellbeing, but also minimise opportunities for fires to occur.”