Exercising in hot weather: how to train at 104 °F (40 °C) without overheating

Exercising in hot weather is doable if you give your body 1–2 weeks to acclimate, train during cooler hours, drink water and know the signs of overheating. When it's 104 °F (40 °C) outside, your usual lunchtime run becomes an ordeal, so summer calls for a different plan: timing, water, clothing and attention to your body's signals. This matters especially in the first weeks of heat or after moving to a hot country.

Can you exercise safely in hot weather?

Yes, but with an adjustment period. Mayo Clinic recommends allowing at least 1–2 weeks to acclimate to heat, and the CDC notes that in the first week you should limit intensity and duration of exercise.

Heat adds its own load: your body has to spend energy cooling down. That's why the same workout feels harder in summer — and that's normal.

How to exercise safely in hot weather outdoors?

The key is choosing cooler hours and places where it's easier to stay cool.

• Train early in the morning or in the evening and avoid the hottest hours of the day.
• Choose shade, parks, breezy waterfronts or a pool.
• Wear light, loose, light-colored clothing, plus a cap or sun hat and sunscreen.
• Cut duration and pace on the first hot days, then build them back gradually.

How much to drink, and do you need electrolytes?

Drink before you get thirsty and bring water to every workout. For moderate exercise, plain water is enough, and for long, intense sessions, drinks with sodium and potassium come in handy.

Don't force yourself to drink — too much water without thirst is risky too. More in "How much water do you really need to drink a day?".

Strength training in hot weather: how to do it?

It's better to move strength workouts in the heat to an air-conditioned gym or a cooler time of day. The load on your muscles is the same, but you should rest longer between sets.

• Lengthen the rest between sets and sip water throughout your workout.
• In the first hot weeks, reduce the volume: fewer sets or lighter weights.
• Keep a towel handy and don't train in direct sun on an open court or lot.

If you're just starting with strength training, the basics are in "Strength training after 40".

How to stay cool, eat and recover after exercising in hot weather?

After a hot workout, the main things are to cool down, rehydrate and eat calmly. Your body spends energy not only on the exercise but on cooling itself, so recovery takes longer in summer.

• Right after your session, get somewhere cool and splash your face or take a cool shower.
• Sip water over the course of an hour instead of downing a whole quart (liter) at once.
• Choose light food with protein, vegetables and water-rich fruits.
• Alternate intense days with easy ones and protect your sleep: on hot nights it's often worse.

Exercising in the heat vs the gym — is indoors safer?

For many people in hot cities, an air-conditioned gym or indoor pool is the most sensible option in peak months. But even there it's important to drink, not push hard right after coming in from the street heat and not forget a light snack, which we wrote about in "What to eat before a workout".

Which overheating signs can't you ignore?

Muscle cramps, nausea, dizziness, headache, severe weakness or vision going dark are reasons to stop right away, get somewhere cool, cool down with a wet towel and drink.

For your first days in a hot country, read "Adapting to a hot climate". For steady energy without caffeine on a hot day, there's Energy Enhancer, and for those who keep training all summer, the X49 patch, which, according to the company, supports endurance in active people.