Rising temperatures alter the marathon playbook
On race day this Sunday, tens of thousands of runners will toe the starting line in a city famous for long distances and ambitious goals. They will confront weather that is warmer than what experts consider optimal for peak marathon performance. While individual sweet spots vary by gender and ability, researchers generally cite an ideal marathon window between 39 and 50 degrees Fahrenheit. That window is becoming harder to hit as the climate warms.
A new analysis from Climate Central, a nonprofit science research group, shows that climate change is steadily eroding the conditions that have long favored record-setting performances. As global temperatures rise due to human-caused emissions, the probability of experiencing ideal race-day weather during major events has declined and will continue to do so in the coming decades.
Global impact: the majority of marathons lose ideal weather days
Climate Central examined 221 global marathons and found that by 2045, 86% are less likely to enjoy ideal conditions on race day. This trend affects marathons across continents and includes all seven Abbott World Marathon Majors. The New York City and Boston Marathons, two of the most storied events in the sport, are among those anticipated to be impacted.
What this means for elite and amateur runners
For elite male runners, the Tokyo Marathon currently offers the best chances of experiencing ideal conditions, but even this event faces a notable decline as temperatures rise. The analysis projects the odds of an ideal day for elite men at Tokyo to drop from 69% to 57% by 2045. In Berlin, the outlook for elite women is grimmer, with chances falling from 40% to 29% for an ideal day. The trend is not isolated to one city; several major races in Boston, London, New York, Chicago, and Berlin show reduced probabilities of hitting the optimal window from 2025 to 2045.
Climate Central notes that while elite female runners are account for a higher resilience to heat, maintaining performance at warmer temperatures, the ideal race-day window for these athletes is still shrinking in decades to come. The broader implication is clear: climate change is reshaping the marathon landscape for runners at all levels.
How heat affects performance and race logistics
Warmer race days influence dehydration risk, electrolyte balance, and pacing. In recent years, heat waves have already forced organizers to alter schedules or provide extra cooling and hydration stations. Dehydration can derail even seasoned competitors, and small miscalculations in fueling or pacing can end a race before it begins. As the climate continues to warm, these challenges will become more common, even for runners who have trained specifically for cooler conditions.
Adaptation strategies for runners and organizers
Experts and former champions urge a two-pronged approach. First, athletes must adapt their preparation and nutrition strategies to a changing climate, including more emphasis on hydration, electrolyte management, and heat acclimation. Nutritionist and coaches stress experimenting with fueling plans that can withstand higher temperatures and extended endurance.
Second, organizers should consider practical changes to race logistics to preserve safety and performance. Potential measures include adjusting start times to cooler parts of the day or increasing early-start options to align with sunrise temperatures. But Climate Central emphasizes that structural solutions require broad, long-term action to curb fossil fuel use and reduce greenhouse gas emissions. Without meaningful climate action, calendar-wide improvements in race-day conditions will remain out of reach.
What athletes are saying and what fans should know
Veteran runners and coaches recognize that the marathon has changed. “Climate change has altered the marathon. Dehydration is a real risk, and simple miscalculations can end a race before it begins,” said Catherine Ndereba, a former marathon world record holder and multiple-time champion. “We’re not just training to run anymore; athletes have to adapt how they deal with the conditions, including in how they eat and hydrate.”
As Sunday’s race unfolds, spectators may notice a shift in strategy—from the pace plans to the cadence of hydration breaks. The underlying reality is that climate change is not distant for marathon runners. It is a daily factor that shapes who crosses the finish line first and who achieves a personal best.
Bottom line: action today for tomorrow’s marathons
Climate Central calls for immediate climate action and a reduction in fossil-fuel use to safeguard the future of marathons. With temperatures likely to trend upward, organizers, athletes, and fans will need to adapt, anticipate, and advocate for resilient race-day planning that keeps runners safe while preserving the sport’s competitive edge.
