Runners Education: Weather Conditions and Winter Running
This is another installation in a series of runners education articles written by UW Health Sports Medicine staff.
Living in Wisconsin provides runners with many challenges for winter training. This is particularly true for runners training for long-distance events. The cold, wind, snow and ice make for a dynamic environment, and runners must be prepared in order to make their runs successful and safe.
Cold-weather training requires a delicate balancing act of anticipating running conditions, selecting appropriate cold weather running attire, and monitoring yourself and your fellow runners for one of several potential injuries related to cold weather.
Note: all temperature references are in Fahrenheit.
Tips to Remember
Any temperature between 60 and 32 degrees can lead to non-freezing, cold weather injuries such as chilblains and hypothermia, especially in wet conditions.
- Any temperature below 32 degrees can lead to freezing injuries such as frostbite and non-freezing injuries such as hypothermia. Risks for these injuries increase below zero degrees and increase significantly below -20 degrees.
- Runners should consider changing to an indoor training activity when temperatures fall below zero degrees and should not perform outdoor training when temperatures fall below -20 degrees.
- Wind significantly changes the temperatures experienced by the human body and wind chill should be factored into training decisions and clothing selection, rather than air temperature alone.
- Runners must add their running speed to the wind speed when calculating the wind chill to accurately represent what the runner will experience when running.
What temperatures are safe to run in?
Thankfully, in the Midwest it is rare that temperatures fall to a low enough level that people should avoid running outside. With appropriate precautions runners are able to train safely during cold weather months on most days. While outdoor activities are generally safe, many people don't realize that any temperature below 60 degrees Fahrenheit has the potential to lead to non-freezing cold weather injuries such as chilblains and trench foot, as well as potentially life-threatening issues such as hypothermia.
Generally, if the weather is cold but otherwise ideal, runners do not experience a significant threat for injury with calm air until the temperature dips below 32 degrees. When the temperature dips below 32 degrees, the danger of sustaining an injury increases but running remains largely safe down to zero degrees as long a winds are calm.
As the temperature gets colder than zero degrees, the need for appropriate clothing becomes more critical, and runners need to consider whether training indoors is more appropriate. Conditions remain relatively safe if appropriate precautions are followed until the temperature reaches -20 degrees. At this temperature or colder, runners should select an alternative to outdoor running becaue the chances of sustaining frostbite are high and can occur with only a few minutes of exposure to the cold air1. While it is possible to train outside in temperatures at or below -20 degrees, runners are strongly discouraged from doing so.
Running during wet conditions such as rain, sleet, or standing water can significantly increase the probability of non-freezing cold injuries. When the temperatures are between 32 and 60 degrees, running in wet conditions must be done with caution, as cold water removes heat from the body at a significantly higher rate than cold air. Moisture in cool or cold conditions can lead to rapid problems with peripheral body parts, skin and ultimately the whole body, which can lead to hypothermia2-3.
Having your fingers exposed to 45-degree air for five minutes can be uncomfortable. Putting your fingers into 45-degree water for five minutes is extremely painful. When training outside in cold and wet conditions, runners should wear clothing that acts as a water barrier and remove wet clothing immediately upon returning to a warm environment.
Wind chill is defined as a still-air temperature that would have the same cooling effect on exposed human skin as a given combination of temperature and wind speed4. So what does that actually mean, how does it work, and why should a runner care?
When the human body is exposed to cold air the body loses heat. That loss is accelerated, however, with cold wind, because cold air repeatedly moves over the skin and steals its warmth. With air that is cold enough and moving fast enough, heat loss can lead to damage to the body - initially to the skin and then other superficial structures. As the body senses these changes, blood flow to these areas decreases, which increases the possibility of significant tissue damage (frostbite) and, with prolonged exposure, the possibility of whole body cooling (hypothermia).
Wind chill is calculated when the temperature drops below 50 degrees F and the wind speed is at least three miles-per-hour1,5. Fifteen-miles-per-hour winds transform a zero-degree day into the equivalent of -19 degrees when wind chill is factored in. Runners can use the National Weather Service website or other online resources to calculate wind chill before training. Runners should avoid running in wind chills at or below -20 degrees and should take extra precautions if the wind chill is between 60 and 32 degrees with rain.
Running Speed and Wind Chill
As the temperature drops, runners must account for their running speed when calculating the wind chill. If the air is calm (no wind), runner speed determines how fast the calm air is moving over the skin - the runner's personal wind speed. To accurately gauge personal wind speed, runners can add the speed at which they are running to the wind speed. Use the chart below to assess your running speed in miles per hour:
|Minutes per mile||Miles per hour|
- Extreme Cold Guide. Center for Disease Control and Prevention. Accessed January 20, 2012
- Castellani, J. Prevention of Cold Injuries During Exercise: Hypothermia. Accessed January 20, 2012
- Hassi, J. Prediction and Prevention of Frostbite. Accessed January 20, 2012
- Merriam-Webster Dictionary. Accessed January 20, 2012
- Windchill Chart and Calculator. Center for Disease Control and Prevention. Accessed January 20, 2012