In this world, magic is very common. For around a thousand years, most people can do magic while those who can't are considered disabled (instead of most people being normal and those who can perform magic being special). However, doing anything extreme with it requires not only training, but expensive 'devices', so the common man is limited in how he uses magic, ie in a rare situation to grant himself a boost of strength.
The cost of magic is: Heat. The more you use it, the more you hit up, and also build up a 'latent heat' ie energy that will slowly be turned to heat in your body over time, even after you've stopped. People who are trained and use it often have a variety of techniques and devices to stop themselves overheating/dying. However, most of these are very specialised, expensive, and inaccessible.
So what 'mundane' and accessible method would every family, say, a rural family have in cases of emergency, say when someone has fought off a predator using enhanced strength, but is now going to overheat, so you need to cool them down quickly? It has to be so common that every house has it, and it should be based on something that we have in our world (I mean, I could as easily introduce a magic heat sponge made from dirt that everyone has, but there's no point in introducing new elements always now, is there? It's always better to let established elements interact with each other in interesting ways to get a solution, instead of handwaving one in)
An example of an emergency provision common in use in real life would be- Basements stocked with supplies in places where tornadoes are common, or fire extinguishers in literally every public building, etc.
SO what would these people use, that's plausible enough? Store lots of ice in an insulated place? Always have a courtyard area with a pool of water built-in?
Note: The world is pre-gunpowder, pre industrial age. So you can't just have a fridge.