|Med City Marathon, about 100 m from the finish|
Overnight, however, the temperature increased, and by the end of the marathon on Sunday it was 85 degrees. In a picture from the end of the race, and you'll notice that none of the twenty-some runners were able to stay in the 3:25 pace group.
Though temperatures in the 40s may sound cool, researchers have found the ideal marathon temperature to be between 41-50 degrees. For every five degrees warmer, times slow by an average of 0.4%. Read more about the in-depth research in, "Everything You Know About Marathons is Wrong," from the New York Times.
In 2015, I paced the Fargo Marathon 3:35 group. The temperature was ideal, the sky was overcast, and the course was flat. I had a large group stick with me for almost the entire race, and several runners finished ahead of me.
How does adjusting for heat translate to training runs? Basically, it means slow down. It's going to take just as much effort to run a slower pace, so don't worry about running as fast as you normally do. If you want a more detailed look at how to adjust your pace, here's a couple of tools:
Runners Connect Temperature Calculator - A simple calculator for adjusting race times
Fellrnr Running Calclator - A more detailed calculator that includes training paces
While they're a nice tool, don't use calculators as gospel truth. Pay attention to how you're feeling, and adjust based on your perceived effort.
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