Climate Change Challenges Marathon Safety
Paul Grinvalds has completed 114 marathons across all 50 U.S. states, yet he struggles with racing in temperatures over 60 degrees Fahrenheit (15.5 Celsius). This challenge affects many runners because the body struggles to cool during exertion, and heat makes this harder.
“Marathoners can be stubborn,” says Grinvalds, 68, from West Des Moines, Iowa. Temperatures even in the 50s F (10 C) feel warm to him. He emphasizes that pursuing marathon goals in such heat often leads to painful or dangerous experiences.
Climate change, mostly due to burning fuels like coal and gasoline, pushes temperatures higher, prompting marathon organizers to take action. To ensure cooler weather, races are being rescheduled, started earlier, or adjusted to allow participants to shorten their runs.
Starting in 2027, the Twin Cities Marathon will move its date from the first Sunday in October to later in the month. This follows the 2023 cancellation and 2025’s high starting temperatures of 70 F (21 C). The Sioux Falls marathon moved from August to September after canceling the 2024 event due to heat. Other races like the Air Force Marathon and Long Beach Marathon have shifted start times to cooler morning hours.
Los Angeles organizers allowed runners to stop after 18 miles and still receive medals, after warm March conditions. Less than 5% chose this option, with only 14 out of approximately 27,000 needing hospital attention, all released the same day. The decision sparked some online debate, but according to spokesperson Meg Treat, runner safety justified the choice.
At the Twin Cities Marathon, race director Ed Whetham called canceling 2023’s event devastating, prompting a permanent move to later dates in October for cooler conditions. The change aims to avoid starting races at 70 degrees (21 C) or higher.
The U.S. experienced its warmest July, with the Earth recording its hottest year in 2024. The World Meteorological Organization projects a temperature rise over 1.5 degrees C (2.7 F) by 2030, worsening marathon conditions. A Climate Central study predicted less favorable marathon climates by 2045 for most U.S. races.
Andy Pershing of Climate Central notes that outdoor exercise faces increasing challenges. Jessica Murfree, from a University of North Carolina-Chapel Hill lab, studies climate impacts on sports. She states that organizers must reconsider event timing and safety in response to climate changes, impacting physical activities beyond organized sports.
Marathons, challenging by nature, become more strenuous under warm, humid conditions. Chris Minson from the University of Oregon highlights an optimal marathon temperature of around 50 degrees (10 C). Body competition for blood supply between muscles and cooling skin complicates exertion in warm conditions.
Exercising regularly in heat allows for better adaptation, though not as effective as cooler conditions. Athletes like John Seals train under extreme heat, even in saunas, preparing for Death Valley’s ultramarathon.
Douglas Casa from the Korey Stringer Institute endorses adjustments like the Twin Cities Marathon’s date change, emphasizing smart, adaptive running strategies in warmer conditions.
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