If you are among the more than 50,000 people who will run the New York City Marathon on Sunday, you know that training, eating right and getting a good night’s sleep are some of the keys to setting a personal best. But an analysis of more than 4.7 million finishing times from 20 years of data on almost 900 marathons — including those in New York, London, Chicago, Boston, Berlin and the Olympics — shows how much your time can be affected by another factor: temperature.

The fastest times are run on days when the average outdoor temperature is in the 40s. (Humidity data were unavailable.) Current weather forecasts suggest that the average temperature in New York on Sunday will be about 61 degrees Fahrenheit (around 16 degrees Celsius), which the data shows will add about 12.5 minutes to the typical finisher’s time, relative to a day in the 40s.

In a sport in which competitors work tirelessly to improve their times by a few seconds, that is a big effect. What’s more, the relationship between temperature and finishing times is actually nonlinear — meaning that the effects of temperature strengthen as it gets warmer.

Temperatures in the 50s increase the typical finishing time by only about five minutes, relative to a day in the 40s. On the other hand, days in the 70s would cause finishing times to be slower by 19 minutes; in the 80s, times would be 33 minutes slower.

And while the biggest impacts show up in the performances of amateurs and weekend warriors, elite runners are not immune to these effects. When considering the top 20 finishing times at the largest marathons, the assessment found that temperatures in the 50s did not slow them, relative to days in the 40s. But temperatures in the 60s and the 70s increased their times by three and four minutes, respectively.

Since temperature has such a big effect on times, would it make sense to adjust official records for the weather? If this were done, five of the 25 fastest men’s marathon times would beat the current adjusted world record. Indeed, three of them would be more than two minutes faster…

Continue reading at The New York Times Upshot…

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