How Cold Is Too Cold to Exercise Outside? (2024)

Coloradans are committed to fitness—sometimes to an extreme degree. Arctic-like temperatures, icy roads, and white-out blizzards aren’t enough to stop Centennial Staters from lacing up for outdoor workouts.

A photo tweeted by CBS Denver reporter Dillion Thomas last month of a man jogging through a snowstorm wearing, well, next to nothing encapsulates this fervor. “There’s a guy running through #Boulder right now wearing socks, shoes, underwear and a beanie,” Thomas said in the post. “That’s all.”

In some ways, this next-level commitment is admirable. In other ways, it feels a bit excessive. Following Denver’s record-breaking cold snap a few weeks ago, which brought sustained negative temperatures, we asked two local doctors how cold is too cold to exercise outside and what Coloradans can do to stay safe in winter-weather workouts.

According to Dr. Rachel Brewer, a youth sports medicine specialist with Rocky Mountain Hospital for Children, there’s no such thing as too cold. “I just say you have the wrong clothes on,” says Brewer, an avid runner who once logged 40 miles in negative 10 degree Farenheit conditions to celebrate her 40th birthday. As long as you’re dressed appropriately for the conditions, exercising in the cold is perfectly safe–no matter how low the thermometer dips, says Brewer.

Dr. William Cornwell, a cardiologist at UCHealth specializing in exercise and sports medicine, agrees most people are OK exercising in extreme cold—so long as they are young and healthy. They may just contend with issues like lung irritation and difficulty breathing caused by cold air passing down their airway, he explains. Another annoying-but-manageable effect of exercising in the cold: Your VO2 max, or the rate of oxygen your body is able to use, decreases starting at 50 degrees Fahrenheit, says Brewer. This means you’ll likely notice worsened performance when exercising in cold weather, though you can counteract some of this effect by dressing appropriately, Brewer adds.

But for other people, including those who have a history of heart or lung disease, as well as those who are at risk for a heart attack, exercising in chilly weather could be dangerous. That’s because the combination of exercise and cold weather can trigger a number of physiological responses that stress the heart and, in some cases, cause a heart attack.

For folks in this category, Cornwell recommends being careful exercising outside in temperatures below 40 degrees Fahrenheit. If temperatures dip below 30 degrees Fahrenheit, he advises exercising inside. Not sure if you’re at risk for a heart attack? Conditions like hypertension, high cholesterol, and diabetes as well as being overweight, middle aged, and male can increase your odds. Cornwell suggests talking with your doctor to narrow down your exact risk.

Now, what happens if you’re young and healthy enough to exercise in the cold, but you don’t wear enough layers—say, you run topless during a snowstorm? For starters, the cold temps can cause blood to shunt away from your extremities and towards your core, which ultimately lowers your muscle efficiency, according to Brewer. If it’s cold enough that you start shivering, your glycogen stores get used up faster, which increases your chances of experiencing a sudden drop in energy levels (a condition known as “bonking”). And, in extreme enough temperatures, you could develop frostbite or hypothermia. The good news: You can combat these physiological changes by donning enough layers.

Brewer recommends investing in a good base layer that is breathable and sweat-wicking, as well as a shell that insulates heat. Quality gloves, a hat, and a buff are also key for protecting your extremities. And if it’s icy out, don’t forget to wear spikes or other traction devices for safety, Brewer adds.

When planning a cold weather workout, Brewer recommends dressing as if it’s 30 degrees warmer than the actual temperature since “too many layers will decrease your performance and comfort with excessive sweating and energy loss.”

Beyond picking the right clothing, Cornwell recommends taking basic precautions to stay safe during winter workouts. “You can alleviate a lot of risk by doing very simple and straightforward things,” he explains. Such things include being mindful of the intensity of your planned workout placed in the context of your risk. For example, if you are at high risk of cardiovascular disease, you probably don’t want to overexert yourself when exercising in the cold. The same goes for exercising at high elevation, which can place additional stress on your heart, explains Cornwell.

It’s also smart to bring extra medication, know where the nearest hospital is in case of an emergency, and let someone know in advance where you’re going and when you plan to be back. If your smartphone or watch has health tracking metrics, like heart rate, blood pressure, and oxygen levels, keep tabs on those during your workout, and understand what numbers would be a sign you should stop exercising.

Lastly, before you gear up for your next big outdoor winter adventure, consider checking in with your doctor to make sure you’re healthy and that you don’t have any unaccounted risk factors, says Dr. Cornwell.

Beyond that, venture outside this season at your peril. Maybe just don’t forget your pants—or shirt.

(Read more: Should You Exercise Outside Today?)