Pairing hydration with carbs and electrolytes like sodium and potassium is important for those who go hard or long in the humidity. That’s because drinking too much plain water pre- or post-workout could lead to a rare but more serious condition known as hyponatremia, which causes an imbalance in sodium blood levels, where sodium is too low. This can cause nausea, headache, or confusion. While this sounds scary, it’s also unlikely to happen for the average exerciser, says Dr. Walrod. (There’s no exact amount of plain water that can cause hyponatremia during exercise, since it also depends on how much sodium you lose in your sweat, but the ACSM recommends maxing out at about 27 ounces per hour to reduce your risk. That’s why if you’re a habitual salty sweater in the heat—one sign of this is if you notice white crystals on your skin after exercising in the heat—it can be even more important to rehydrate with electrolytes, as SELF reported previously.)
2. Start slow—and keep your intensity low.
The good news about exercising in the humidity is that it does get a little easier over time. Heat acclimation occurs when your body adapts to heat stress, which can take at least seven days of frequent exercise, Dr. Walrod says. The more regularly you get out there, the more efficient the acclimation will be, though there will still likely be a benefit from less frequent exercise.
So what should you do during this time? As you’re allowing your body to adjust to the hot, humid weather, Dr. Walrod recommends cutting back on the intensity and the duration of your workout. That can look like bringing your pace slower by a minute or so, and cutting the distance of your typical runs in half.
It may also be helpful to warm up in a non-humid environment during this acclimation period—say, by trying this quick warm-up routine in the comfort of your air-conditioned home before edging outdoors. While warming up outside may seem like a smart way to adjust your body to the heat, you’re actually raising your core temperature more than you need to, which jumpstarts the impacts of the humid environment on the body, says Dr. Pistilli.
Once your body is acclimated and you start to feel the effects of humidity less intensely, you can go closer to your typical duration and intensity, but you should still be mindful of the humidity and heat of the day. In other words, be ready to make adjustments.
“Take breaks and listen to your body,” Dr. Walford says. “If it happens to be humid, just try to go slower.” In these conditions, he believes your body should go 10 to 15% slower than your usual pace. Oftentimes, your body will intuitively slow down to handle the change in the environment, so be mindful of what it’s telling you—and don’t try to overrule it.
3. Time your exercise to beat the humidity.
There are two things to think about when considering your outdoor summer workout: the humidity and the actual temperature. The sun’s rays are strongest midday, which can make the temperature feel hottest then. But relative humidity is actually highest in the morning when the air temperature is cooler and more saturated with water. It’s lowest in the afternoon, when air temperature is the highest.
The best way to schedule your workout, then, is considering a measure that takes both of these things into account. It’s called the heat index, which is what the temperature feels like when combining relative humidity with the air temperature, Paul Chase, Ph.D., an assistant clinical professor of exercise physiology at Ohio University, tells SELF. If the reading is over 90, that means you should proceed with caution, he says. In that case, especially if you had an intense exercise session on tap, you’re likely better off swapping it for an at-home or gym workout in the comfort of the air conditioning.
4. Always wear sunscreen.
Wearing sunscreen is not only important while exercising under the hot, beating sun to prevent a sunburn, but it also plays a role in cooling: Burned skin doesn’t cool as efficiently, according to Dr. Chase.