Los Alamitos cancelled the Friday program after the second race after the jockeys said conditions were too hot to continue the eight-race program.
The cancellation was announced at approximately 2 p.m., when the horses for the third race were in the paddock.
The temperature was approximately 100 degrees.
The Quarter Horse and lower level Thoroughbred meeting is scheduled for this evening.
Daytime Thoroughbred racing is scheduled for Saturday afternoon, although another hot day is forecast.