Heat, Humidity, Dew Point and the 15 Mile Run

It has been hot in Iowa lately. It seems summer has finally made an appearance in the midwest, and for runners it has been a harsh reminder to pay attention to the elements.

Kara, Doug, and I met at Raccoon River Park to get our weekend long run in. We were planning on 18 miles, and at the start everything seemed right with the world. Clear skies, calm winds, and at 7:30 am the temps were great. Raccoon River Park is a nice 3 mile loop around a lake, with a partially paved path turning into packed dirt and crushed gravel. There are some open areas, some nicely shaded areas, and a beautiful view of the lake at almost every step.

We took off and our first three-mile loop was rather easy. We stopped for a quick restroom break, and headed out for the second loop. As we ran we noticed that with the suns rising, the humidity was increasing. It started to get uncomfortable quickly, but we forged ahead and got another 6 miles in before needing to stop for more water. With no wind, it started to feel like a sauna, yet me decided to go on. At mile 12, I told Kara and Doug to go on ahead, as I needed to walk a bit. I did a walk/run pattern until I was close to 15 miles.

That’s when Kara, who was way ahead of me, texted saying that she was stopping at 15 miles. It was too humid to continue on. I texted back saying that I would be at our starting point in a few minutes.

While it was frustrating to not get the 18 miles in, I have to remember that heat, humidity, and dew point affect runs as much as snow, sleet, and bitter cold do. We have been lucky as midwestern runners with a mild summer and almost perfect running conditions. But, as today proved, we need to understand what effects weather has on our performance.

Here is a chart from Runnerworld.com that shows how the dew point affects a runner, and when we should call it a day.


While we were in the ‘uncomfortable for most people’ zone, it was good that we listened to our bodies and didn’t push it. Tomorrow is another day, and we have another 6 weeks until we taper for the marathon. I think all three of us were glad to get out of the heat.

Please remember to stay hydrated, and to listen to your body.

Live healthy, be happy!