What Temperature Is Dangerous for Running?

Knowing how hot is too hot to run can save you from serious health trouble.
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Runners can be hardcore when it comes to keeping up with their training schedules, even when the weather is dangerous. When a race is on the line -- or you’re just dead set on getting faster and fitter -- it can be tempting to head outdoors in extremely hot or cold temperatures. However, doing so can have severe health consequences. Instead of jeopardizing your health and body, learn the temperature limits for running outside and only do what you can do. Save the rest of the training for the treadmill.

Extreme Heat

    Running in the heat is just part of the drill during the summer, but there are days when it’s too much for your body. The National Weather Service (NWS) offers a chart outlining your risk for experiencing heat disorders while running in certain temperatures based on relative humidity. When the humidity is low, your body is better able to cool itself and you can safely run in higher temperatures. When the humidity is high, your sweat doesn’t evaporate as quickly, making your body’s cooling method less effective and your inner temperature rise. When the relative humidity reaches 90 to 100 percent, extreme caution should be used starting at 82 degrees and higher. However, when the relative humidity is at 40 percent or lower the extreme caution level doesn't begin until the thermometer hits 90. Temperatures and conditions within that range should be considered threatening, and, regardless of the humidity, caution should be used in all temperatures above 80 degrees.

Heat Dangers

    If you choose to run in hot weather, you risk experiencing heat-related health problems, including dehydration, muscle cramps, heat exhaustion and heatstroke. As your body temperature rises, your internal tissues literally begin to cook. Without action, this can lead to fatal results. Muscle cramps can be treated by rehydrating, cooling down and removing yourself from the sun. Heat exhaustion is characterized by symptoms like dizziness, nausea, fatigue, headaches, lack of coordination and vomiting, and should be treated immediately with fluids, a cool environment, elevated feet and potential medical attention. Heatstroke, which occurs when your body temperature rises to 105 degrees or higher, is a medical emergency characterized by hot and dry skin, disorientation, weakness or unconsciousness and must be treated with immediate cooling treatment, rehydration and medical attention.

Extreme Cold

    Similar to a dangerous heat index, a strong wind chill plays the greatest role in how cold is too cold when it comes to running. According to the National Weather Service, under calm conditions frostbite becomes a threat within 30 minutes only when the air temperature reaches -10 degrees. A 60-mph wind, however, makes frostbite a threat within 30 minutes at 10 degrees. With that same high-wind speed, frostbite can occur within 5 minutes if the temperature drops to -10 degrees.

Cold Dangers

    Health concerns from running in extreme cold include frostbite, in which unprotected body surfaces freeze, and hypothermia. Conditions such as wind and slick surfaces force you to run more slowly in the cold, which lowers your metabolic heat production and causes your body temperature to drop. Once your temperature dips below 95 degrees, you experience hypothermia, and your heart, nervous system and other organs will stop functioning properly. If left untreated, this can lead to heart and respiratory failure or even death.

Tips and Cautions

    Opting to run on a treadmill during extreme temperatures can spare you from dealing with temperature-related health concerns. If you do choose to go out, however, be sure to dress appropriately, covering as much skin as possible in cold and wearing sweat-wicking, breathable clothes in the heat. Run routes close to home in case problems occur, and stay hydrated during intense heat. If you start to feel symptoms of heat or cold-related health problems, stop immediately and treat your condition.

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