El Niño and Marathons: How Heat Impacts PRs and Chicago
A study of 1.8M results warns about 2027 climate, while Yara Achôa recounts a hot race in Chicago.
A forecast of a strong El Niño raises alarms for runners chasing a personal record over 26.2 miles. Radar Stemma examines the climate data alongside real-world challenges and triumphs at the Chicago Marathon.
Chasing a marathon personal record (PR) requires months of meticulous training, carefully selected gear, and tailored nutrition plans. However, one uncontrollable factor can alter everything: the weather. An analysis pooling nearly 1.8 million marathon results revealed that performance steadily drops as temperatures rise, affecting amateur runners most severely. With a historically intense El Niño phenomenon forecast for 2027, athletes targeting ambitious goals will need to pay close attention to both race dates and average temperatures.
Atypical Heat in Major Marathons
The impact of elevated temperatures is not a distant concern. Recent editions of traditionally fast races, including Berlin and London, have already experienced unseasonably hot days that challenged entire fields. At the Chicago Marathon, temperatures also caught runners off guard who anticipated the crisp, cool autumn weather typical of the US Midwest, forcing immediate adjustments to pacing and hydration.
Journalist and runner Yara Achôa experienced these conditions firsthand after starting her race at 8:30 a.m. in Chicago. Leaving her warm layers untouched in her luggage due to the unexpected heat, the race demanded extraordinary resilience. Beyond the weather, her challenges began before race morning: a bout of flu during travel week and sleepless nights took a heavy physical and mental toll early on the course.
Overcoming 26.2 Miles and the Meaning of the Race
Within the first two kilometers, an unprecedented panic attack and shortness of breath nearly derailed her journey. After regaining mental and physical composure, her strategy shifted to alternating between running and walking intervals. She crossed the finish line in 5:05 — roughly 40 minutes over her target training pace — but celebrated the accomplishment of finishing.
Despite initial frustration with the clock on Chicago's famously flat course, the value of the experience ultimately triumphed. Enthusiastic crowd support in the final miles, encouragement from coaches stationed along the route, and the presence of family along the course gave fresh meaning to the effort. As runners often reflect, fluctuations and adversity are central to the marathon experience: when pacing plans collide with heat and the unexpected, crossing the finish line remains the greatest victory.