You could try visualising yourself in cool or cold water or ice for a certain amount of time. If by heating up you mean that you (from memory) expand energy from your spinal cord (practitioners who are good enough can stand naked in a waterfall and keep warm), then (if it is not dangerous to do) you could maybe try safely to do the opposite, or "breathe in" a small amount of cool or cold energy, or better breathe it to be around you, rather than in you. Start small so you can get a feel for it safely. These are just ideas.
You could also try Elements, if you are able to handle them - carefully and very slowly invoke a small amount of water for cooling effects. Elemental work can be dangerous, so if you haven't the experience, either don't do it or do one or two breaths only, to be able to gauge it.
https://www.satanisgod.org/www.angelfire.com/empire/serpentis666/Invoking_Elements.html
https://www.satanisgod.org/www.angelfire.com/empire/serpentis666/Preparing.html
https://web.archive.org/web/20150915063748/https://www.angelfire.com/hailtosatansvictory666/More_Info_Elements.html
https://www.satanisgod.org/www.angelfire.com/empire/serpentis666/Invoking_Water.html