I like heat. I even like humidity. (Dry air send my throat, eyes, nasal passages into a panic.) I also like watching tennis which around here happens in the dead heat of summer. My favorite social media comment ever was a guy yelling at the tournament account that they shouldn't hold tennis tournaments when it's going to rain. And well, we really need that rain when the heat index is triple digits.
1. Be in the AC is the obvious option. But sure you might need to run errands, watch a sporting match of some sort, mow the lawn, or have an outdoor job.
2. Hydrate. I know. Everyone says this. But all the extra things your body needs to do during extreme weather need liquid.
3. Be a shade seeker. Know where the shade is, whether it's the shadier side of the street to walk down, the shadiest spot to leave your car, the shadiest spot to wait for the bus, find the shade. You can also carry an umbrella or wear a large brim hat and create some of your own shade. If you do, be mindful of others. Being poked when it's stupid hot is harder to handle.
4. Take breaks. You may have a great vantage that just happens to be in full sun right now. Plan out a break that takes you to a cool spot. Sip water, snack, watch from the concourse a bit. If you are out running errands and the stores you are hitting are not sufficiently cool, stop in at a cooling center or library (or combo cooling center library). Know where these things are along your route.
5. Natural fibers are really breathable. Athletic type clothes may also have sweat wicking capabilities. If you are somewhere you cannot alter your clothes, just keep this in mind and plan for breaks as much as you can.
6. Know the signs of heat stroke and heat exhaustion: https://www.nhs.uk/conditions/heat-exhaustion-heatstroke/
Dizzy is bad and means you need to take steps now. Heart racing is bad and means you may need medical attention. Don't worry about being embarrassed, I promise if you pass out you will be more embarrassed.
7. Think of heat like staying up all night. You can do it, but it takes effort. Small breaks help if you can't get longer breaks. And missing some of the fun is worth it to avoid missing the rest because you had to go to the ER instead.