Tag Archives: Heat Index

The ideal running temperature vs most people’s ideal temperature

One thing I find annoying is right before a relatively warm race when the obnoxious race emcee says, “It’s a perfect day outside for a race!” You can clearly tell from such a statement that the guy never runs, ever.

Because while 60-70 degrees feels amazing if you’re out for an easy walk, or laying out in the sun… that temperature enters the somewhat-warm zone for distance runners in a race, who are moving a lot faster than a walk and producing a lot of body heat throughout their run. Add in substantial humidity, which interferes with the evaporation of sweat, and now it begins to feel really hot.

Jonathan Savage created a ‘perceived heat index for runners’ calculator to accurately show what a runner’s “heat index” is for a given pace at their height and weight, depending on the temperature and humidity.

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As you can see, 65 degrees at even a mild 40% humidity can feel like 101 degrees Fahrenheit for a runner my size (5’10”, 160 lbs) running at a 9:05/mile pace.

To be fair, that’s mild compared to how most of the summer has felt for me, running in 80-95 degree afternoons with 60-75% humidity. Even running at slower paces, my heat indices have been in the 130-145 degree range. Needless to say, that has prepared me fairly well for the worst heat this Sunday’s Chicago Marathon could offer me.

Thankfully, the forecast indicates it won’t get that bad. Projected temperatures are slated around 60-65 degrees for the race, with overcast and 80-90% humidity due to a sizable rainstorm slated to hit Saturday (and BTW Chicago runners, might want to get that shakeout run in early during the brief moments it’s not raining).

The heat index for race day could be anywhere from 100-115 degrees depending on what the temperature is, but it’s still milder than I’ve experienced all summer, plus it will be pretty much overcast so the sun won’t be adding to the heat that much.

In any case, I’m not big on clapbacks or “educating” people, but the next time someone attempts to point out that 60+ degree weather is perfect running weather, you may want to throw some knowledge at them about how running changes everything.

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