About the analysis

This data interactive explores which races are projected to remain record-breaking contenders — and which are losing their competitive edge — as global temperatures continue to rise.

Methodology

We looked at temperature conditions on the days of 221 marathons worldwide in 2025: all seven Abbott World Marathon Majors, all races sanctioned by World Athletics, and a representative set of races across Europe, Canada, and the United States.

Using our Climate Shift Index system, we found the probability of each race day reaching temperatures at optimal running conditions — in other words, what the chances are that a runner will experience the ideal temperature for their skill level and gender on the day of their marathon. We calculated those probabilities for 2025 and used climate projections to estimate the probability in 2035 and 2045.

The two skill levels analyzed are referred to as “elite” runners and “recreational” runners — elite refers to the top 1% of runners, and recreational refers to the median runner, whose marathon times fall at the middle of the pack.

We analyzed the probabilities using the daily average temperature (average of the day’s high and low temperatures). This specific temperature typically occurs in the late morning, and is a good proxy for conditions encountered by most runners in most races. We also calculated the probabilities based on daily low temperatures, which typically occur near sunrise. This represents one adaptation option of switching to an earlier start time.

See the full methodology for more details.

Contributions

Lead Analyst: Andy Pershing
Writer: Arielle Tannenbaum
Editor: Raina DeFonza
Designer: Megan Martin
Data visualization: Kaitlyn Trudeau, Brandon Bourassa, Helen Brush

Climate Central is an independent group of scientists and communicators who research and report the facts about our changing climate and how it affects people’s lives. Climate Central is a policy-neutral 501(c)(3) nonprofit.

Contact us

For questions about the analysis, or to request an interview with a climate scientist, please email Abbie Veitch at aveitch@climatecentral.org