Are you dehydrated?
Lick yourself after a run to see how dehydrated your are. If it’s really salty, you’ll need to replenish electrolytes. And you’ll often find that the more acclimated you become to running in warm weather, the less salty you’ll be. Dehydration can be mild, moderate, or severe based on how much of the body’s fluid is lost or not replenished. When it is severe, dehydration is a life-threatening emergency.