Seeking cool threads (for staying cool during the heat dome)

Summer is already gobbling up most of Europe and is about to start on north america with earnest this weekend.  

Let's gather up our favourite threads about staying cool in hot weather.  


And yes, i have ulterior motives of helping the daily-ish team gather up often overlooked threads.

My favourite, cooling the person, not the space
https://permies.com/t/57366/Cool-person-space-methods

And saving money on electricity in the summer
https://permies.com/t/4017/ways-reduce-summer-utility-bills