A forecast for extreme temperatures has forced racing officials to shift Saturday's Moonee Valley race meeting to a twilight timeslot.

The Bureau of Meteorology says temperatures are expected to reach 41 degrees before an expected cool change in the early evening.

Racing will now start at 4.35pm instead of 1.30pm and there will be free entry for racegoers.

Racing Victoria's Paul Bloodworth said the decision to push the meeting back three hours had been made in the interests of safety.

"The safety and wellbeing of our equine and human participants is our first priority in reviewing meetings in hot weather conditions," the governing body's racing operations manager said.

"We have been consulting closely with the Bureau of Meteorology and temperatures will be high tomorrow from the early morning so bringing the meeting forward wouldn't provide any relief for our participants.

"However, a cool change is expected to reach Melbourne in the early evening so commencing the meeting at the later time means the majority of the race card should be run in more comfortable conditions."

A picnic race meeting at Dederang in north-east Victoria will go ahead with stewards and veterinarians to monitor conditions.