My running advice for you for dealing with heat and humidity is: RUN SLOWER! What’s the hurry? Someone has to be contrarian and confront the mindless madness of just always running faster than we should for weather conditions. Speed is great if we are intelligent about how we use it in workouts but not everyday. Yes, we have fast-twitch muscles but we all have slow-twitch muscles too. And we all need some slower runs to provide some restful recovery and to counterbalance the faster runs. Run efficiently, gently, and comfortably on slow run days!
If the humidity is above 75-80% or higher (maybe even about 65%), just don’t push the pace when running (unless you are racing) or you will crash and burn. If it’s warm, slow down a tiny bit. If you push the pace too much when it’s hot and humid, you can get dehydrated or worse. Heatstroke, heat exhaustion, etc. Be mindful of running an appropriate pace for the conditions in which you are running. Don’t run on autopilot when it’s hot and/or humid! Keep your brain plugged in! Also beware of mysterious sudden (calf) cramps when you run faster than your legs think you should for conditions. (This usually happens to me at least 2-3 times per summer. Or more.)
Too hot and humid during your run? Take a walk break, as often as you need it. Drink some water. Hydrate and rehydrate. Don’t dehydrate.
Fringe benefits of running slower: You will see things you won’t see when you are running too fast (faster than zippity-doo-dah pace).
For example, here’s a baby turtle from today’s run.I saw the ground moving (or it appeared to be). Made me do a double-take. Stopping, I realized something green was moving. Or was it just a shell? Surprise! It was a baby turtle shell. My efforts to photograph this amazing little animal were frustrated by his fear of me and his desire to run (or slide?) away from someone who might consider him prey. But I assure you I do not hunt or chase turtles (except for catching them on camera). I realized that if I had not been running slow, humidity-adjusted turtle pace today, I might not have seen him. Or I may have stepped on him (he was trying to run/slide on the trail but sauntered to the grass at a turtlishly slow pace when he saw me).
So my personal challenge to each of you reading this is to schedule some turtle-paced runs where you run/walk and/or adjust the pace by 1-3 minutes slower than an all-out effort. Conversational pace. Can you talk and/or sing songs while running without being out of breath? If you succeed, Yertl the Turtle will be very happy!