Running

I live in the subtropics in Asia, it's 30-35C during the day most of the year and humidity often in the 90s. I've tried exercising outside many, many times. I've talked to many other people, many of them trainers with a lot of experience. It takes some experience to know when you're just experiencing exertion, or you're in actual trouble with heat stress.

So for a beginner it's already tough to take up running in a hot place, much more so in a place that's hot and humid, where your sweat doesn't evaporate much, if at all. By the time you realize you're in trouble, if you do, you may have trouble getting to a place where you can cool down properly. Plain shade won't do in the humidity, as I'm guessing you've noticed. You just keep sweating and sweating but it doesn't cool your body down.