Rising Heat Threatens the Future of Record-Breaking Marathons

A new study by Climate Central has revealed that global warming is tightening the window for record-breaking marathon performances, with 86% of the world’s 221 major marathons projected to experience less-than-ideal running conditions by 2045.

The report, released just before the 2025 New York City Marathon, highlights how rising temperatures are reshaping the sport — making it increasingly difficult for elite athletes to achieve peak performance.

The “sweet spot” for marathon running sits between 39°F for men and 50°F for women, but those conditions are becoming rare as heat waves push race-day temperatures higher.

Even top-tier events like the Berlin and Tokyo Marathons have recently faced unseasonal heat, forcing organizers to consider earlier start times.

Runners such as Britain’s Mhairi Maclennan and Kenya’s Catherine Ndereba warn that climate change is not only altering competition but threatening the very possibility of record-breaking runs.

As marathoners adapt with stricter hydration, revised training, and earlier race schedules, experts warn that without global climate action, endurance running itself could face a crisis where even the strongest strides fall short of their potential.