This Month’s Heat is Showing Us the Future of Sports

For the last two weeks, ultra-endurance athlete Lael Wilcox has been attempting to break the world time record for circumnavigating the globe on a bicycle. Her 18,000-mile route has already seen her bike from Chicago, through Ontario, and out to the Atlantic coast of Canada. The past few days, she has been cycling through record-breaking hot weather in France, with temperatures more than 10 degrees above normal for this time of year. On Sunday, June 21, after three thousand miles of cycling and several days of heat exhaustion, she decided to end her world record attempt because the risk to her health from the heat was too severe.

The heat wave that ended Lael Wilcox’s world record bid was no mere natural weather phenomenon. Europe is a hotspot for rising extreme heat and the nonprofit Climate Central estimates that climate change made the current extreme temperatures in France at least four times more likely than they would have been otherwise. In the hypothetical world in which humanity had rapidly transitioned away from fossil fuels, the heat wave hitting Europe might have been mild enough to allow a highly conditioned athlete—one who has already circumnavigated the globe on a bike before—to cycle through it. But now, even the most elite athletes on the planet cannot withstand the deadly heat conditions that are a window into our hotter future.

The signs of our rapidly changing planet in the sports world are not limited to Europe. The National Park Service recently announced that at least three hikers have already died this June from heat exposure in the Grand Canyon. Earlier this year, the heat at the French Open overwhelmed world No. 1 Jannik Sinner, sending him to an early exit in the second round.

And even before the ongoing World Cup in the U.S., Canada, and Mexico began, dangerous combinations of heat and humidity were forecast to affect many of the games. Even though this year’s tournament has added hydration breaks for players, an analysis by the Guardian found that the games already played in Miami and Monterrey took place at temperatures that should have triggered delays or additional mitigation measures.

Heat and humidity place fundamental thermodynamic limits on the human body. Human health requires maintaining homeostasis, and high ambient temperatures prevent the body from dissipating heat and maintaining stable internal temperatures. If exposure to high temperatures is sustained, core temperature rises, and cardiovascular and renal collapse can occur. These conditions can be fatal in serious cases, especially for older individuals or those with comorbidities.

Even the scientific research on climate change has not fully accounted for the myriad risks that heat poses to athletes, fans, and sports staff. In 2023, my collaborators and I showed that climate change had already increased the number of home runs hit in Major League Baseball, because warmer air is less dense and thus poses less air resistance to a batted ball. We were able to perform this analysis because MLB loves to collect data on itself, so we have decades of information on every home run hit in every game. But it is much more difficult to track how individual players, game attendees, or stadium staff are being affected by the sweltering conditions that now dominate many American summers.

One thing is clear, however: As long as humanity continues to emit greenhouse gases, the risk of deadly heat will continue to rise. Every increment of global warming, even a tenth of a degree, is associated with a greater frequency of hot days and a greater intensity of major heat waves. And as global fossil fuel emissions hit a record high in 2025, these trends should be expected to continue. This year’s heat will become normal within the coming decades.

To safeguard the health of athletes, fans, and staff, sports will have to change accordingly. Air conditioning in some of the World Cup stadiums this year has been helpful, and building domes on baseball stadiums has become the norm in hot states like Texas. Moving kickoff times to the evening, a measure already undertaken in some World Cup games, will be increasingly necessary to avoid playing games in the hottest parts of the day.

For ultra-endurance athletes like Lael Wilcox or skilled players like Jannik Sinner, heat waves are no longer simply an obstacle to be overcome through mental and physical toughness. They may serve as direct barriers to major sports milestones, as even the most well-supported athletes cannot push their bodies beyond the fundamental limits imposed by thermodynamics.

Across multiple sports over the last several months, the world has witnessed the toll that heat can take on the performance of the most elite among us. Unfortunately, this pattern isn’t an aberration. As long as humanity continues to emit greenhouse gases, what we’ve seen recently will serve only as a window into our new normal.