An OT (of course) recently introduced me to phase change cooling clothing and the tech is so interesting!

Unlike water ice packs that take forever to freeze and then are so cold that you can only safely touch them for 10 minutes at a time, some genius made gel packs that freeze at 15C. So you can freeze them in the fridge and then wear them continuously for hours without frostbite.

They are pricey but there aren't many other options for people who need to be outside in the heat.