Climate Matters: Extreme heat on Opening Day allows baseballs to fly farther

The 2026 Major League Baseball Opening Day in St. Louis is forecast to be impacted by extremely hot weather that could challenge century-old records. A historic heat dome that has stalled over the Desert Southwest for days is expanding east and bringing more record-breaking temperatures to the central U.S. for late March.

Temperatures for the St. Louis Cardinals game on Thursday are expected to reach or exceed 90 degrees, threatening the daily record of 87 degrees set in 1991 and the all-time hottest March temperature of 92 degrees set in 1929. Tipoff in the midafternoon will expose players and fans to the worst of the heat.

The forecast comes as baseball season temperatures across 26 MLB cities have warmed by an average of 2.8 degrees Fahrenheit since 1970, according to Climate Central. Los Angeles, home of the Angels and Dodgers, is the lone exception and experienced no change in baseball season temperatures since 1970.

Scientists have linked this warming trend to a measurable increase in home runs, as warmer air is less dense and allows batted balls to fly farther. A 2023 study found that global warming affects air density, which has caused a small but significant increase in home runs.

Research shows that a one degree Celsius (1.8 degrees Fahrenheit) increase in temperatures in open-air stadiums leads to a 2% increase in home runs per game. This effect is slightly larger for afternoon games and smaller for night games.

The study also found that human-induced climate change led to an average of 58 additional home runs per year between 2010 and 2019, totaling 577 over that decade. This accounts for approximately 1% of all home runs during that time period. While other factors like performance-enhancing drugs, refined training, and player skill have contributed to more home runs, scientists say rising temperatures and lower air density also played a role.

Higher temperatures increase the risk of heat-related illness for athletes, staff, and spectators; extreme heat is the deadliest weather-related hazard in the United States. All 26 U.S. cities that host Major League Baseball teams are now experiencing an average of 13 more extremely hot days annually compared to 1970.

These effects could triple by the 2050s. Under a scenario where global carbon pollution is curbed, an estimated 182 home runs could be added annually, about a 3% increase compared to the average in the 2010s. In the long term, the increase in home runs could influence team strategies, player acquisition, and public engagement with the sport.