Racing at Caulfield on Wednesday will start an hour earlier than planned because of predicted high temperatures.

A high of 40C is expected in Melbourne on Wednesday with the Caulfield meeting to start at midday and the last race to be run at 4pm.

Racing Victoria (RV) had already brought start times for Wangaratta's meeting on Tuesday forward, with that meeting to kick off at 11am with the last event at 2.45pm in an attempt to avoid the forecast peak temperature of 42C at 4pm.

The temperature at Wangaratta was monitored on Monday and the decision was made to proceed with Tuesday's meeting from the amended start time.

"The safety and welfare of equine and human participants is of paramount concern to Racing Victoria in assessing whether a race meeting should proceed in hot weather conditions," RV's racing operations manager Paul Bloodworth said.

"After monitoring the forecast and assessing the temperature at Wangaratta today, we made the decision to proceed with the meeting which is scheduled to conclude 1-1/4 hours prior to the predicted hottest part of the day.

"By reducing race intervals and commencing from 11am the bulk of the meeting will be staged while temperatures range between 30 and 39 degrees."

RV will review the status of meetings for the rest of the week, with hot weather expected for the next four days.

Stewards will monitor the weather conditions and the welfare of jockeys and horses at the race meetings with the option to call the meetings off if needed.

The government has issued a heat health alert ahead of a week in which temperatures are expected to top 40C on Tuesday, Thursday and Friday.