Running Out of Cool Days

The report finds that 86% of analyzed global marathons will see a decline in the odds of optimal running conditions by 2045. While elite women are more resilient to heat, elite men are most affected, particularly at the Tokyo Marathon, which is projected to see the largest decline in ideal conditions among the Abbott World Marathon Majors. The analysis highlights that the 2025 Tokyo and Berlin Marathons experienced unusual heat made two to three times more likely by climate change. Shifting race start times to sunrise is identified as a potential adaptation to increase the likelihood of optimal temperatures for most runners.

• Of the 221 global marathons analyzed, 86% (190 races) are projected to experience a decrease in the probability of optimal running conditions for either elite or recreational runners by 2045, including all seven Abbott World Marathon Majors.
• Among the Abbott World Marathon Majors, the Tokyo Marathon has the highest current probability of ideal conditions for elite men (69%) but is projected to face the steepest decline for this group, dropping to 57% by 2045.
• Elite female runners exhibit higher temperature tolerance than other groups, and for some races like Boston and Tokyo, warming may actually slightly increase their odds of optimal conditions between 2025 and 2045.
• Human-caused climate change significantly increased the likelihood of extreme heat during the 2025 Tokyo and Berlin Marathons, making the unusual warmth three times and two times more likely, respectively.
• Moving race start times to earlier in the day (near sunrise) could mitigate warming impacts for most runners; for example, it would increase the 2045 probability of peak conditions for elite men in London from 17% to 61%.

APA

Pershing, A., Tannenbaum, A., DeFonza, R., Veitch, A., Dahl, K., Martin, M., Trudeau, K., Bourassa, B., & Brush, H. (2025). Running Out of Cool Days. Climate Central. https://assets.ctfassets.net/cxgxgstp8r5d/4FQz6CuX6a2bOAhYf43sel/9b0dd0c433f189dcd2be24939d7a8223/Running_Out_of_Cool_Days__How_climate_change_is_decreasing_the_odds_of_optimal_marathon_conditions.pdf

Chicago

Pershing, Andy, Arielle Tannenbaum, Raina DeFonza, Abbie Veitch, Kristina Dahl, Megan Martin, Kaitlyn Trudeau, Brandon Bourassa, and Helen Brush. Running Out of Cool Days. Climate Central, 2025. https://assets.ctfassets.net/cxgxgstp8r5d/4FQz6CuX6a2bOAhYf43sel/9b0dd0c433f189dcd2be24939d7a8223/Running_Out_of_Cool_Days__How_climate_change_is_decreasing_the_odds_of_optimal_marathon_conditions.pdf.

Wikipedia

{{cite report |last1=Pershing |first1=Andy |last2=Tannenbaum |first2=Arielle |last3=DeFonza |first3=Raina |last4=Veitch |first4=Abbie |last5=Dahl |first5=Kristina |last6=Martin |first6=Megan |last7=Trudeau |first7=Kaitlyn |last8=Bourassa |first8=Brandon |last9=Brush |first9=Helen |title=Running Out of Cool Days |publisher=Climate Central |date=28 October 2025 |url=https://assets.ctfassets.net/cxgxgstp8r5d/4FQz6CuX6a2bOAhYf43sel/9b0dd0c433f189dcd2be24939d7a8223/Running_Out_of_Cool_Days__How_climate_change_is_decreasing_the_odds_of_optimal_marathon_conditions.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{pershing2025running, author = {Pershing, Andy and Tannenbaum, Arielle and DeFonza, Raina and Veitch, Abbie and Dahl, Kristina and Martin, Megan and Trudeau, Kaitlyn and Bourassa, Brandon and Brush, Helen}, title = {{Running Out of Cool Days}}, institution = {Climate Central}, year = {2025}, month = oct, url = {https://assets.ctfassets.net/cxgxgstp8r5d/4FQz6CuX6a2bOAhYf43sel/9b0dd0c433f189dcd2be24939d7a8223/Running_Out_of_Cool_Days__How_climate_change_is_decreasing_the_odds_of_optimal_marathon_conditions.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }