Urban Heat Hot Spots in 65 Cities

Climate Central analysis of 221 marathons indicates that the probability of optimal, cool race-day temperatures is decreasing due to global warming. For recreational runners in the U.S., the current average chance of optimal temperatures is 27%, and this is projected to decline in 46 of 51 analyzed U.S. marathons by 2045 if high levels of heat-trapping pollution continue. The analysis highlights regional disparities, with the Northwest having the best current odds (55%) and the Southwest the worst (14%). Beyond performance, the document notes that rising heat and humidity increase risks of heat-related illness and that climate-driven air quality issues, such as wildfire smoke, further threaten runner health.

• Recreational runners in U.S. marathons currently face a low probability of racing in optimal temperatures, averaging 27%. Only seven of the 51 analyzed U.S. marathons have a greater than 50% chance of optimal temperatures, with the highest probabilities found in Seattle (79%), Boston (74%), and Anchorage (73%).
• Regional differences are stark, with recreational runners having the best current odds of optimal temperatures in the Northwest (55%) and the worst in the Southwest (14%). Marathons in Honolulu, Hawaii and Miami, Florida are described as having virtually no chance of optimal temperatures.
• Under a scenario of continued high heat-trapping pollution, optimal race-day temperatures are projected to become less likely by 2045 in 46 of the 51 analyzed U.S. marathons. The most significant decreases are expected in Eugene, Oregon (10 percentage point drop) and Anchorage, Alaska (15 percentage point drop).
• At the TCS New York City Marathon, the probability of ideal temperatures is projected to decrease by two to five percentage points for all runner types by 2045. This would result in a 27% to 29% chance for recreational runners and a 17% to 66% chance for elite runners.
• Rising temperatures and humidity increase the risk of heat-related illnesses, such as heat stroke and heat exhaustion. Additionally, climate change increases the frequency of events that degrade air quality, such as wildfires, which produce fine particulate matter that can cause inflamed airways and labored breathing for runners.

APA

Climate Central (2025). Urban Heat Hot Spots in 65 Cities. https://www.climatecentral.org/climate-matters/marathons-2025

Chicago

Climate Central. Urban Heat Hot Spots in 65 Cities. 2025. https://www.climatecentral.org/climate-matters/marathons-2025.

Wikipedia

{{cite report |author=Climate Central |title=Urban Heat Hot Spots in 65 Cities |date=28 October 2025 |url=https://www.climatecentral.org/climate-matters/marathons-2025 |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{climatecentral2025urban, author = {{Climate Central}}, title = {{Urban Heat Hot Spots in 65 Cities}}, institution = {Climate Central}, year = {2025}, month = oct, url = {https://www.climatecentral.org/climate-matters/marathons-2025}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }