I live on an island in the Caribbean, around 90 degrees year round. I mostly running early mornings and evenings to stay out of the heat. Once the sun comes up, I get tired really fast, to the point where I have to stop to take a breather. It's like I get overheated. Any way to deal with this?
Thomas, I live in Dallas, where we've had a blistering summer, almost two months of days with highs in the 103-106 degree range (with high humidity almost daily) and overnight temps not dropping below 83-84 degrees. On August 14th, we had a half marathon called the Hottest Half, which I spent most of June and July training for, so I think I can offer some tips.
Hydrate like crazy. Drink enough water so that your urine is very pale all of the time. Fill the water/drink bottles you carry on your run halfway and freeze them, then top them off before you run. You'll have something cool to drink for a good part of your run that way. Keep a cooler with iced water or sports drink near the end point of your run so that you can cool down your core temp more quickly when you finish your run.
Dress cool. Light colors, lightweight wicking fabrics. Cover your head with a light colored cap. Wear sunscreen and reapply as necessary.
Start early. Head out no later than dawn, because it's only going to get warmer from there.
Go slowly. Don't push yourself too hard because it is too easy to overheat and cook your brain. Even if you survive a bout of heat stroke, you might not be the same mentally.
Run on trails instead of roads. The ground absorbs/reflects less sun and heat than roads and sidewalks, and trails tend to be shadier.
Running in the heat is dangerous. Be very aware of how you're feeling and don't try to "tough it out" if you start feeling nauseous or mentally fuzzy. Better to walk a bit or cut your run short than to risk your life and health.