One thing that has changed my world in summer is having a UV parasol! It's portable shade and stops me from being overstimulated by the intense heat of the sun on my skin. Also means I don't have to put on as much suncream because I'm not in the sun. Neck fans or handheld fans can help a lot as well... I hear you though, I struggle immensely in the heat and humidity and it's likely going to continue now until September which is a bit worrying

I've found that cold packs on the neck, wrist or back can really help, but I know that some people can't tolerate that for long periods of time!