Another polar vortex has drifted down over the country this week. Here on just the other side of Lake Michigan from Chicago, our wind chills will drop into the negative 40 Fahrenheit range. For even the heartiest of runners, the dangerously cold wind chills raise the question “how cold is too cold to run outside?”
If you ask runners this question, the answers will widely vary. I asked the question in my Instagram stories and received answers ranging from 40 degrees to “frostbitey cold.” I love running in 10 to 20-degree temperatures. Some runners refuse to run in anything below freezing. Other runners will claim that there’s no such thing as bad weather, just bad gear. But what about beyond preference? Is there actually a threshold at which it is physically unsafe to run? (As a note: all references to temperature in this post are in Fahrenheit unless otherwise noted.)
How Cold is Too Cold to Run?
The windchill matters as much as the actual temperature. There is a significant difference between 10 degrees and sunny with little wind and 10 degrees but overcast with 20mph winds. When looking at the conditions, always consider the wind chills.
In terms of performance, you cannot expect to run the same pace when the wind chills drop to zero Fahrenheit or below – even if you are properly dressed. In frigid conditions, your body prioritizes blood flow to your core in order to protect your vital organs. As a result, your extremities – including your working muscles – receive less blood flow and the blood vessels constrict. Without normal blood flow to your working muscles, you cannot expect to run like you would in milder temperatures.
Beyond performance, health concerns arise in frigid conditions. Sub-zero temperatures pose risks such as hypothermia and frostbite.
Hypothermia becomes a concern in negative temperatures. Hypothermia occurs when your core temperature dips below 95 degrees. In frigid sub-zero temperatures, the risk of hypothermia occurs within just 30 to 60 minutes – the average amount of time you would spend on a run. Wind chills reaching well below zero can increase the risk of hypothermia. The symptoms of hypothermia can range from extreme shivering and blue fingernails (in mild cases) to shallow breathing, exhaustion, confusion, loss of coordintion, slurred speech, and a weak pulse.
Frostbite poses another risk. The colder it is, the higher the risk; the risk of frostbite increases when the temperatures drop below minus 5 degrees Fahrenheit/-20 Celsius. Once the wind chill reaches below minus 16 degrees, frostbite on exposed skin can occur within 30 minutes. The colder it gets, the shorter amount of time it takes for frostbite to happen.
What I always consider in any aspect of running are the risks versus the rewards. What are the risks of running outside in the extreme cold? Do they outweigh the benefits of a single run (or, in very bad conditions, a week of training)?
Ultimately, you have to respect your personal comfort zone. Just because someone on Instagram ran in 10 below F temperatures doesn’t mean you have to. If you do not feel comfortable running outdoors in the cold, stick to the treadmill or indoor track, or cross-train instead. There is no shame in using the treadmill! And if the temperatures are so far below zero that you do not even want to leave the house, take a rest day or do an indoor workout from the warmth of home.
Personally? After examining the evidence, I would not run in anything colder than a negative 5-degree F wind chill. Any colder than that and run is not worth the risk of frostbite and hypothermia. Others will have different conclusions than I do – some will head indoors much sooner and some will run in even colder conditions.
If you are going to run outdoors in very cold temperatures – whatever those are to you – optimize your safety and performance with the following tips:
Warm Up Indoors
You do not want to break a sweat in this warm-up since anything damp against your skin can increase the risk of hypothermia. The purpose of an indoor warm-up is to start sending oxygen-rich blood to your working muscles and improve your range of motion before you head into the cold.
Try a simple warm-up such as this pre-run warm-up or one of these dynamic warm-ups for runners. Do your warm-up right before you head out the door.
If you are going to run when the wind chill dips below zero, you need to take precautions in how you dress. Wear wicking layers that will keep you warm and help you stay dry. If it is very windy, top off with a wind-resistant jacket. Cover up as much exposed skin as possible to prevent frostbite. Mittens, neck gaiters, hats, tall socks, and balaclavas can protect sensitive areas. Even if it’s not very sunny out, sunglasses or even ski goggles can protect your eyes from the sting of the cold and wind. Duct tape your shoes to prevent heat loss.
Eat Well and Hydrate Before Your Run
When you run in very cold temperatures, you are asking a lot of your body – so provide it with the resources it needs. While running in the cold does not necessarily burn more calories, an empty stomach is not to your advantage. Running in the cold relies more on aerobic metabolism using carbohydrates (vs aerobic metabolism using fats). Your body needs available energy to run in the cold.
Hydration is essential also. The cold can mask thirst, but the dry air can be dehydrating. As you run in dry air, your body loses fluids as it works to humidify the dry air.
Run by Time Instead of Distance
The combination of the cold, wind, ice, and snow will slow you down. If you run 5 miles in 45 minutes in normal conditions, then run for 45 minutes – without worrying about pace – in the cold conditions. Training by time ensures you get the same benefits of the run (45 min at an easy pace is the same no matter how far you go!) while also accounting for conditions affecting your pace.
Easy runs are a better option in the bitter cold. Snow and ice often accompany sub-zero temperatures. Even if you find a clear stretch, the cold can increase the risk for pulling a muscle or tendon.
Be Flexible in Your Training
Your training plan should not dictate your life. During bad winter weather, adjust your training plan as needed. If the weather is ideal one day, try doing your long run or hard workout that day. If it’s too cold to run outside, either take a rest day, cross-train, or adapt your run for the treadmill.
Try one of these treadmill workouts for runners or, if you are training for a race, these race-specific treadmill workouts. If you have to do a long run, try these tips for surviving a long run on the treadmill.
Running in the Cold with Dogs and Kids
If the wind chill reaches below zero, leave your dog at home. They are more sensitive to the cold than humans, even with booties and a jacket. Sub-zero temperatures are certainly not the weather to take an infant or toddler out in a jogging stroller. Just because you can bundle up and tolerate bitter windchills as an adult doesn’t mean your pets or child can.
Linking up with Coaches’ Corner!
How cold do you consider too cold to run outside?
What’s the coldest you have ever run in?
With the temps that the Midwest is getting right now, my butt would be inside on the treadmill or track. It’s just not worth it to feel miserable. Not to mention how hard it is to warm up afterwards. I’ll run in single digits with a wind chill below zero but it depends on the distance and what my goal is for the run. Easy running is all that I’ll do outside in frigid temps. Stay warm!
Thank you! It’s so cold here that my gym is even closed, so even the track and treadmill are not an option here! Warming up after a frigid run is the worst part – it can be harder than the run itself!
I am certainly a winter warrior but these are just ridiculous temps right now! I think I am going to have to take it indoor for a few days
When 10 degrees feels warm in comparison, you know the temperatures are ridiculous!
My threshold for longer runs is around 10F – any colder than that, and I’m just too uncomfortable in the later miles for it to be worth it. I’ve done some shorter runs when it’s been in the single digits, and with enough layers I’ve been ok – but I feel like the Michelin man in those cases 🙂
Minnesota is so cold today that they even suspended our mail service (current air temp this morning is -28!!). Even though I don’t love the treadmill, I’m thankful my gym has remained open so far!
There is a point where if you can bundle up enough, those are just too many layers to comfortably wear on a run!
As much as I love seeing photos of runners with frozen eyelashes (so pretty, really) I just can’t imagine running in the negative temperatures. Fortunately, that will never be a problem for me! I’m so glad I live in a desert! Stay safe when you run in this crazy weather!
The frozen eyelashes are pretty but they never feel too good!
I usually run outside as long as the streets are not icy. Monday is was a feel like -6, but there was very little wind, and it was fine, I was actually overdressed. The wind plays a much larger role for me in the winter than the temp does. I’m in NE Ohio, so we’re dealing with the polar vortex. My butt was at the fitness center running countless laps around the small indoor track.
The wind (or absence of it) makes a huge difference when it’s that cold!
10 degrees including the wind chill is kind of my threshold also. Wind speed is really the more critical factor though. If it’s over 15 mph and less than 32 degrees it can be miserable that one direction. I love being outside and if the paths aren’t clear enough to run I’ll snowshoe or cross country ski. Otherwise I will be inside. My gym is closed today too but I did strength and cross training at home rather than go out in the -40 degree wind chill.
Winds over 15mph in winter are brutal – no matter what point in the run you are running into them!
Really great tips! I think we’re going to have some negative degree wind chills over the next couple of days! Wearing the right amount of clothing and protecting the extremities is so important with the weather so cold! I need to find some good wool socks to stay warm out there!
Wool socks make a huge difference! I wear Darn Tough Vermont on the coldest days and haven’t dealt with numb toes yet.
I have definitely run in some super cold temps when I wad training for Boston which is sometimes not fun. The gear is definitely key as well as hydration and fueling beforehand and during. Time to layer up!
Extra attention to hydration is so crucial in winter – but it’s rough when water bottles freeze on a run!
These are all great tips. Personally, I can’t take running on the treadmill or in the gym, so outside is just always what I do – hot or cold. Living in Minnesota, where a below zero windchill is pretty normal in the winter, I’m just used to it. I would say that the temps we’re having today (-27 with a -51 degree windchill) are too cold for me to run outside, but honestly, anything up to a -35 windchill is okay with me. You’ve just got to make sure every little bit of you is covered, your layers are windproof and warm, and you don’t stay out too long!
That’s impressive how cold of windchills you can handle!
Great tips. It has to be really cold before I retreat to the treadmill due to temperature. It hasn’t gotten there this winter. Yet.
I agree – the treadmill is a resort only after it’s too cold or too icy to be outside. Even when it’s cold, the fresh air feels so good!
It’s never too cold for running. I’m the person who runs in t-shirts and shorts in winter too unless the temperature drops below 15F.