QUESTION: How hot is too hot to be out riding my bike? I came home the other day from an afternoon ride and felt a little sick for the rest of the afternoon, with no appetite. – Arnold W
RBR’S STAN PURDUM REPLIES: If you’re looking for a number, start with a feels-like temperature of 90 degrees (Fahrenheit), which is about where many forecasters start warning about dangerous heat, but several factors can move that limit up or down.
Feels-like temperature takes into account not only the ambient air temperature, but also the relative humidity and wind speed to determine how weather conditions feel to bare skin. As such, it’s a better measure of what effect the weather is likely to have on you.
For example, here are the projected air and feels-like temps in my area for this June day, according to weather.com:
|Time of day||Air temp||Feels-like temp|
Clearly, if I want to ride today, it would be better to ride in the morning than in mid afternoon or evening.
Bear in mind, however, that these numbers don’t account for the fact that road cyclists are usually riding on blacktop, which on high-temp days can get hot enough to fry food, and which radiates heat, raising the temperature of the air immediately above it. So road riders can assume their feels-like temperature (as well as the actual temperature) is a bit higher.
The factors that can move the “too hot” limit up or down include:
- Fitness. This refers not only to your general health, but also to your overall athletic condition. The better your fitness, the greater the likelihood you can handle higher temps when riding.
- Heat you are used to. People who regularly work out in higher temperatures adjust to it to some extent and can usually tolerate more heat than those who aren’t accustomed to such efforts.
- Shade. You may have some routes that have more shade than others, and on a blazing hot day, you can choose one of those. For example, near me is a paved trail that is in shade most of its distance. And there’s enough leafy canopy that it’s sheltered from the sun almost all day. The temperature on that trail can be as much as 10 degrees lower than it is in direct sunlight. On very hot days, I can still ride that trail.
- Terrain. Pumping up hills raises your body temp a lot, and the downhill cruise that follows usually isn’t long enough to dissipate all the heat. So choose a flatter route on hot days. If, however, you need to ride hills, be prepared to stop frequently — even on the way up — to let your body temp return to normal.
- Flexible distance rides. A friend of mine has a “hot day” loop route of about 10 miles that includes two parallel mostly flat country roads with some connecting roads that make for easy shortening of the ride. He drives to the loop and is never more than a few miles from his car. If he’s handling the heat well, he pedals the whole loop two or three times. If the heat becomes too intense, he shortcuts on a connecting road and gets back to his car quickly.
While “feels-like” is a useful number for deciding when it’s too hot to ride, here are a few other weather-measuring scales that you may find helpful as well:
Heat Index. A chart that uses both air temperature and humidity to arrive at a number that gives a better indication of how the weather will affect you. For example, if the temperature is 90 but the humidity is 70%, the heat index number is 106 degrees. But if the humidity is only 5%, the heat index is 84 degrees. The heat index is calculated in the shade, however, which limits its accuracy for riding on the road.
RealFeel. This is AccuWeather.com’s proprietary “feels-like” temperature that considers humidity, cloud cover, winds, sun intensity and angle of the sun when arriving at a number. The latter measurement is useful in determining what time of day to ride, since the angle of sun at different times of day determines how intensely its heat is felt.
Wet Bulb Globe Temperature. A parameter that estimates the effect of air temperature, relative humidity, wind and solar radiation. Often used by the governments, military, OSHA and athletic organizations to manage workload of individuals in direct sunlight. See more here.
If you are riding in hot weather often, it’s a good idea to keep a chart with the air temp and feels-like temps and notes on how you felt and performed under those conditions. The chart will help you on subsequent days when deciding whether it’s too hot to ride.
Stan Purdum has ridden several long-distance bike trips, including an across-America ride recounted in his book Roll Around Heaven All Day, and a trek on U.S. 62, from Niagara Falls, New York, to El Paso, Texas, the subject of his book Playing in Traffic. Stan, a freelance writer and editor, lives in Ohio. See more at www.StanPurdum.com.