1) Battle of bands events 2) Certain competitions 3) Early races 4) Events in battle of bands 5) Finals preceders 6) Increases molecular motion 7) Makes warm 8) Meet preliminaries 9) Meet prelims 10) Microwaves 11) Nukes, so to speak 12) Pops in the microwave 13) Preliminaries at a track meet 14) Preliminary contests Found on https://www.crosswordclues.com/clue/heats
In Olympic competition, events consist of four heats. The winner is determined by the lowest combined time for the four heats. Prior to Olympic competition, each sled is permitted six training runs on the Olympic course. Found on https://www.encyclo.co.uk/local/21309