Harness Racing Victoria made the decision after gathering information from its Extreme Weather Policy, the Victorian Government and agencies such as the Country Fire Authority and Vic Emergencies.

Temperatures are tipped to reach 40 degrees in Horsham on Thursday and the fire danger in the Wimmera is rated as "extreme".

"The welfare of our horses and participants is of highest importance and certainly comes before the desire to race," HRV CEO Matt Isaacs said.

"This is a case of common sense prevailing over all else."

Racing will continue as planned in Shepparton on Thursday night.