Racing Against the Heat: How Marathons Are Adapting to a Warming Climate

When Paul Grinvalds lines up for his 115th marathon, he isn’t just thinking about mileage; he’s eyeing the thermometer. At 68, the West Des Moines veteran has finished a race in every state, but even a gentle 55°F can feel sweltering to his seasoned body.

“We’re stubborn,” Grinvalds jokes, wiping sweat from his brow. “If it’s hot we still chase the goal, and that’s just plain stupid because you end up hurting yourself.” His candid confession echoes a growing worry among distance runners: a warming planet is turning a classic 26.2‑mile challenge into a potentially dangerous heat trial.

Race officials are taking note. Starting in 2027, the Twin Cities Marathon will abandon its long‑standing first‑Sunday‑of‑October slot and slip a few weeks later. The move follows a 2023 cancellation after record heat and humidity made the start line feel more like a sauna than a finish line. A cooler October morning, even if it risks an occasional snowflake, is preferred to a 70°F kickoff.

South Dakota’s Sioux Falls Marathon made a similar pivot, shifting from August to September after a blistering 2024 edition forced a shutdown. Out West, the Long Beach Marathon and the Air Force Marathon in Dayton now launch before sunrise, hoping that the pre‑dawn chill will buy runners a few precious degrees.

Los Angeles tried something different in March 2025: runners could voluntarily stop after 18 miles and still earn a finisher’s medal. Fewer than five percent took the shortcut, and only 14 of roughly 27,000 participants needed hospital care—none stayed overnight. Still, the decision sparked a lively online debate about fairness versus safety.

“We listen to the feedback,” said Meg Treat, a spokesperson for the LA event. “Our priority is keeping runners safe, and the numbers show it worked.” The sentiment is shared by Ed Whetham, director of the Twin Cities Marathon, who called the 2023 cancellation “devastating.” A deeper look at climate trends convinced him that a later October date dramatically improves the odds of a cool, fast race.

Science backs the organizers’ gut feelings. A Climate Central study of 221 U.S. marathons predicts that by 2045, 46 of the 51 races they examined will no longer enjoy the ideal low‑40s °F conditions that recreational runners crave. Andy Pershing, the study’s lead author, warned, “Our ability to run outside, stay healthy, and enjoy sport is being challenged by climate change.”

With July 2024 already the warmest on record for the contiguous United States and 2024 the hottest year globally, the pressure to adapt is only growing. Marathon committees are now in a race of their own—scrambling to redesign calendars, tweak start times, and sometimes even reimagine the distance—all to keep the sport alive under an increasingly hot sky.