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Running in the Heat - How to Avoid Heat Exhaustion

Updated: Aug 27, 2023

As a runner, you probably know that the summer heat can be dangerous. But how do you know when to avoid running in the heat?


In this article, we'll help you with making the decision, of whether it's safe to run or if you should avoid the heat altogether.



When to Avoid Running in the Heat


When you should avoid running in the heat:

  • 85 Degrees or Higher

85 degrees may not seem or feel hot to you. But it's important to not underestimate the sun's rays. It's just like laying out in the summer on a cloudy day. People may underestimate the intensity of the UV and you can get sunburnt.


So if you decide to go for a run try to avoid routes that constantly expose you to the sun. Take breaks in a shaded area. Run early in the morning or later in the day when temperatures have cooled off a little and the sun's UV index is below 5.

  • 80% Humidity or Higher

Another situation in which you don't want to underestimate the weather is when it's really humid. The additional moisture in the air makes the "feel like" temperature hotter than it actually is. Again, in times like these, consider getting in an early run or waiting till later in the day when things are a little cooler.


  • Acclimate

Over time your body can adapt to the weather conditions but it's important to ease into it. Take hiking Everest for example, you can't make the venture in one straight shot. Your body needs time to adjust to the altitude and low oxygen levels. It's the same for summer runs, your body needs time to adjust to the heat.


If you find yourself having a difficult time acclimating to the heat then take it even slower. If you are uncomfortable consider other options where you can still get in a workout in a more comfortable/tolerable environment.


How to Avoid Heat Exhaustion

  • Light Colored Clothes

  • Lightweight Attire

  • Sweat-Wicking Attire

  • Hat

  • Sunglasses

  • Sunscreen

Make sure you drink plenty of water. Don't go into a workout in a dehydrated state. If you are planning on working out outdoors on a hot day, drink water throughout the day, during your workout, and after to replenish lost fluids. Avoid wearing dark clothes, especially black. Wear sweat-wicking clothes and a hat (if you are not a hat person then you may want to opt for sunscreen and maybe sunglasses).


Heat Index: How to Calculate the Heat Index


The heat index is a measure of how hot it feels when both the relative humidity and air temperature are combined. The heat index is usually higher than the air temperature because evaporating sweat can cool you off.


The heat index changes with time, so one cannot be certain what the current heat index reading will be during any given run. The National Weather Service provides an hourly forecast for your area that includes both current air temperature and wind speed, but there's no way to predict when weather conditions will change abruptly.


An alternative method for calculating heat index involves measuring wet bulb globe temperature instead of dry bulb thermometer readings (or vice versa). Scientists have determined that this measure correlates more closely with human discomfort than either dry or wet bulbs alone. In humid areas where evaporation rates aren't as high as they would be under drier conditions due to higher relative humidity levels."


Running in the Heat


The heat can make running more dangerous, but there are ways you can run safely.

  • Progression

Your first run out in the heat will most likely be the toughest workout. Don't focus on your pace or time, just focus on your body and how it handles the heat. Guage your workout, maybe you need to back it off a little bit.


Your second run, maybe even your third, fourth, etc. run will be tough but slightly easier than the prior workout. This is good, this is progress. Patience is key and knowing your body, your limitations, and your strengths.

  • Fluids

Summer heat and humidity put you at greater risk of developing dehydration if you don't carefully monitor your fluid intake. Does your body need water or electrolytes? What nutrition does your body need, sweet or salty substances? Running in extreme heat requires more energy expenditure and making smart choices.


  • Preparation

Are you carrying a water bottle on short runs or a pack on long runs? Are you carrying gels or some other source of nutrients with you? Is there shade coverage on your route or are you exposed to the sun for a vast majority of the time?


How to Run in the Heat


The best way to stay healthy and safe when running in the heat is by listening to your body, taking breaks when necessary, and staying hydrated. If you feel like something is off, take a break from running for a few days. Heat-related illness can be avoided if you listen to your body's signals and avoid pushing yourself past your limits when exercising outside during the summer months.

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