Apply sunscreen liberally and often for skin protection, as solar radiation causes skin cancer.  Remember to apply it to any exposed skin – including your ears, scalp, and back of your neck.  Don’t forget to wear a hat, sunglasses, and a shirt. 


Running in the heat will increase sweating in order to dissipate heat and keep your core temperature from rising too quickly.  Increased sweating (without replacing fluid lost thru sweat) will decrease your blood volume, which in turn, will decrease blood and oxygen delivery to your working leg muscles, eventually slowing you down.  Drinking fluids to keep your blood volume up will offset this effect and enhance your performance.  But be careful – as drinking too much can create other issues, including GI distress/bloating and hyponatremia (low blood sodium). For most runners during a training run or race, drinking when you are thirsty (ad libidum) is reasonable and effective.  If your run route doesn't have ample water fountains, then consider carrying a water bottle on your long run days.  Finally, it’s as important to keep yourself hydrated throughout the day when not running as it is during your runs.  Having a hydration plan throughout the day will help keep your total body water stores replenished and thus, similar to fueling a gas tank in a car, you’ll be starting your runs off with your blood volume “full” instead of closer to “empty.”   The current general recommendation is to drink ~9-13 cups of fluid per day (which is a bit more than the adage of eight 8-ounce glasses per day).  This recommendation should be increased in hotter climates and exercising individuals. 


Are you accustomed to running in hot weather? Practice running in the heat in preparation for hot weather races.  It generally takes about two weeks to properly acclimatize to exercising in hot weather.  To begin acclimatizing, slow your pace (don’t do speed workouts or harder efforts) during that first week of warmer weather training, stay well-hydrated, and schedule adequate rest/recovery time. 


Avoid running during the hottest part of the day.  Listen to your body and stop exercising, find a shaded, cool area, and rehydrate (+/- seek medical attention) if you experience lightheadedness, headaches, or you stop sweating.  Wear light colored clothing to reflect the sun’s rays.  Synthetic fabrics are better for exercising as they wick and dry easier, taking heat away from your body and helping you to stay cool.


Your body reacts differently on hot days. You won’t be able to perform as well in the heat as you could on a cooler day, so slow your pace during training runs and races on such hot days.

Authored by UW Medicine Sports Medicine Physicians
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