ABSTRACT

Marathon organizers across the United States are moving race dates, starting events earlier, and offering shortened courses in response to increasingly warm conditions that researchers and race officials say pose growing risks to runner safety, according to athletes, academics, and race directors interviewed by the Associated Press.

ABC News Australia

Marathon organizers shift dates and start times as rising temperatures threaten runner safety

Aug 15, 2026, 2:52 PM

Context

The contiguous US recorded its warmest July ever this year, and the Earth had its hottest year on record in 2024, according to the source. The World Meteorological Organization forecasts that between 2025 and 2030 the Earth's average global temperature will likely rise by more than 1.5C compared to the 1800s.

A study of 221 races by the climate research group Climate Central found that warming is already making conditions worse for most marathons. By 2045, optimal conditions for recreational runners — 6 to 7C — would be less likely at 46 of the 51 US marathons analysed.

Several US marathons have already made scheduling changes. Organizers of the Sioux Falls, South Dakota, marathon moved their annual race from August to September after cancelling the 2024 race due to hot conditions. The Air Force Marathon in Dayton, Ohio, the Little Rock Marathon in Arkansas, and the Long Beach Marathon in Southern California have moved start times to earlier in the morning. The Twin Cities Marathon permanently delayed its race by a couple of weeks following the cancellation of its 2023 event.

At the Los Angeles marathon in March, warm conditions prompted organizers to give runners the option of stopping after 18 miles and still receiving a finisher's medal. Less than 5 percent of participants chose the shorter finish, and only 14 of roughly 27,000 runners were treated at a hospital, with all released the same day. The offer drew online criticism.

Physiologically, running a marathon in warm conditions is difficult because the body must simultaneously supply blood to working muscles and route blood to the skin for cooling. University of Oregon professor Chris Minson, who researches how people adapt to extreme heat, said the optimum temperature to run a marathon is about 10C, and that only about 25 percent of the energy expended during rapid movement is used to propel the body forward, with the remainder going toward managing the heat produced by that movement. High humidity compounds the problem by preventing sweat from evaporating.

All Perspectives

Paul Grinvalds, marathon runner: "One thing about marathoners is typically we're kind of stubborn. So if we have a goal and it's hot, a lot of times we're still going to try to do that goal, which is just stupid because you're almost guaranteed to have a very painful experience."

Meg Treat, Los Angeles Marathon spokesperson: "We welcome the feedback and it's certainly something that caused a lot of discussion, but when we're grading ourselves on it, it has to do with how safe our runners were on the day of the event and we're very happy with the outcome."

Ed Whetham, Twin Cities Marathon race director: Whetham called the decision to cancel the 2023 marathon "devastating" for runners and the organisation, and said it prompted an extensive weather-pattern analysis that led to permanently delaying the race by a couple of weeks. He said: "We'll take a 39-degree (4C) start over a 70-degree (21C) start."

Andy Pershing, Climate Central: "The ability to go outside, to exercise, to take advantage of your human body and being healthy, that's something that's getting challenged by climate change."

Jessica Murfree, University of North Carolina-Chapel Hill: Murfree said organizers of marathons, bicycle races, and other competitions — from tennis to college American football — increasingly must consider changing event dates and times and adopting other safety measures as climate change makes weather hotter and more volatile. She said the concern extends to whether people can get outside on increasingly warm days at all, asking: "If we can't walk, if we can't exercise or go for runs, it's too hot, can we still stay physically active while remaining cool?"

Chris Minson, University of Oregon professor: "As you get to warmer temperatures you end up having a bigger competition between blood supplying your muscles to keep running, to keep nutrition going, and blood flow to your skin for thermal regulation." Minson also said that by regularly exercising in warm weather, people can acclimate to high temperatures and perform better in the heat, though likely not as well as in cooler conditions.

Douglas Casa, Korey Stringer Institute: Casa called the Twin Cities Marathon's scheduling change prudent, and said: "If someone was smart enough to say, 'OK, it's a little hotter today than usual, I'm going to run a 7-minute mile instead of a 6:30 mile,' then they won't get any hotter than normal. It's just that runners are sometimes very locked into what they normally do and what their goals are."

Gaps & Unknowns

The source does not state the specific temperatures recorded at the races where scheduling changes were made.
The source does not state the total number of participants in the Sioux Falls, Twin Cities, or other affected marathons.
The source does not state whether any runner deaths or serious injuries have been directly attributed to heat at the races described.
The source does not state the methodology or sample composition of the Climate Central study beyond the number of races examined.
The source does not state whether the Climate Central study has been peer-reviewed.
The source does not state what criteria the Los Angeles Marathon used to determine warm conditions warranted offering the shortened course option.

Sources & Further Reading

ABC News Australia — original

Read the original at ABC News Australia

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