Climate Matters
More Extremely Hot Days for School Sports
Young athletes heading back to practice this summer could face more extreme heat hazards.
Climate Matters•July 2, 2025
Baseball Season Heating Up
KEY FACTS
Baseball season is heating up. Since 1970, average temperatures during the Major League Baseball (MLB) season have warmed by 2.8°F on average across the 27 MLB cities.
Warming seasons aren’t the only way that climate change affects players and fans of America’s pastime.
Warmer air is less dense, helping batted baseballs fly farther. This effect is driving a measurable increase in home runs.
A recent study found that warming caused by climate change added an average of 58 MLB home runs per year over the 2010-2019 period — about a 1% increase.
The effect of warming on home runs could triple by the 2050s — adding 182 home runs annually in a scenario that assumes global goals to reduce planet-warming carbon pollution are met.
This Climate Matters analysis is based on open-access data from the National Oceanic and Atmospheric Administration (NOAA). See Methodology for details.
Download data
Baseball season is heating up
As the climate warms, baseball season is heating up — affecting players, fans, and even home runs.
Climate Central analyzed temperature trends in every Major League Baseball (MLB) city from 1970 to 2024. See Methodology for details.
All but one of the 27 MLB cities have warmed during baseball season (March 30 – Oct 1). On average, the 26 warming MLB cities have seen average temperatures rise by 2.8°F during the season.
The exception was Los Angeles, home of the Angels and Dodgers, which experienced no change in baseball season temperatures since 1970.
The top 10 warming MLB cities are:
Team | City | Baseball season warming, 1970-2024 |
|---|---|---|
1. Toronto Blue Jays | Toronto | 5.4°F |
2. Arizona Diamondbacks | Phoenix, Ariz. | 5°F |
3. Houston Astros | Houston, Texas | 4.3°F |
4. Cleveland Guardians | Cleveland, Ohio | 3.6°F |
5. Detroit Tigers | Detroit, Mich. | 3.6°F |
6. Milwaukee Brewers | Milwaukee, Wisc. | 3.6°F |
7. St. Louis Cardinals | St. Louis, Mo. | 3.6°F |
8. Texas Rangers | Dallas-Fort Worth, Texas | 3.5°F |
9. Atlanta Braves | Atlanta, Ga. | 3.4°F |
10. Tampa Bay Rays | Tampa Area, Fla. | 3.3°F |
As average temperatures warm, extreme heat occurs more often — putting players and fans at risk.
All 26 MLB cities in the U.S. are also experiencing an average of 13 more extremely hot days annually than they did in 1970.
Extreme heat is risky — from Little League to MLB
Sports and extreme heat can be a dangerous mix. Heat is the deadliest weather-related hazard in the U.S. And athletes are among those most at risk.
Exercising or playing sports outdoors in extreme heat can add increased stress to athletes' bodies, putting them at risk of dehydration and heat-related illness.
An intense early summer 2025 heat wave sent multiple MLB players off the field with heat exhaustion and illness.
According to Climate Central’s Climate Shift Index, the high average temperatures on those game days were made at least two times more likely by human-caused climate change at both Busch Stadium in St. Louis and Wrigley Field in Chicago.
As our climate warms, the rise in extreme heat is a growing concern among all athletes — from professionals to student athletes heading back to practice in late summer across the U.S.
Extreme heat can also put ballpark staff and spectators at risk — particularly during outdoor day games.
Warmer, less dense air helps baseballs fly farther
Warming seasons aren’t the only way that climate change affects players and fans of America’s pastime.
Warmer air is less dense and therefore exerts less drag on batted baseballs, allowing them to fly farther.
The number of home runs per game has increased since the 1980s. While many factors – including the use of performance-enhancing drugs and changes in analytics and player training – have likely contributed to the documented rise in home runs, science suggests that rising game day temperatures and decreasing air density over the same period are playing a measurable role.
Home runs are an exciting part of baseball, and can change the course of a game in an instant. But rising home run rates have implications beyond the scoreboard. Over the long term, more home runs can potentially affect gameplay, strategy, player acquisition, and public engagement with the sport.
Warming has caused a 1% rise in MLB home runs in recent years
A 2023 study found that warming — through its effect on air density — has in fact caused a significant (albeit small) increase in MLB home runs.
The study found that a 1°C (1.8°F) increase in daily high temperatures on game days in open-air stadiums leads to a 2% increase in home runs per game. This effect is slightly larger for day games played in the early afternoon and smaller for night games.
Between 2010 and 2019, human-caused warming led to an average of 58 additional home runs per year, or 577 in total. This is a statistically significant but small effect, accounting for about 1% of all home runs during the same time period.
Ongoing research is testing various explanations for the leading causes of the recent surge in home runs.
More home runs in a warmer future
Although the influence of warming on home runs to date is small, the effect is real and is expected to increase with future warming (in the absence of future gameplay changes such as more domed or night games).
The effect of warming on home runs could triple by the 2050s — adding 182 home runs annually under projections that assume global pledged commitments to reduce planet-warming pollution are met. This represents about a 3% increase relative to the recent (2010-2019) annual average.
But many countries are failing to meet their commitments to reduce pollution. In alternate scenarios with very high levels of pollution and future warming, the MLB could see a 9% increase in home runs annually by the end of the century (2090s).
Baseball leagues could adapt to some extent by scheduling more night games or building more ballpark domes, but our warming climate will continue to add home runs to America’s pastime — potentially altering gameplay, strategy, public engagement, and the business of baseball.
CONTACT EXPERTS
Andrew Grundstein, Ph.D.
Professor, Department of Geography
University of Georgia
Related expertise: Climate and human health, heat vulnerability
Contact: andrewg@uga.edu
William M. Adams, Ph.D.
Adjunct Associate Professor, Department of Kinesiology
University of North Carolina at Greensboro
Related expertise: Exertional heat stress
Contact: wmadams@uncg.edu, william.adams2486@gmail.com, wmadams@msu.edu
FIND EXPERTS
Submit a request to SciLine from the American Association for the Advancement of Science or to the Climate Data Concierge from Columbia University. These free services rapidly connect journalists to relevant scientific experts.
Browse maps of climate experts and services at regional NOAA, USDA, and Department of the Interior offices.
Explore databases such as 500 Women Scientists, BIPOC Climate and Energy Justice PhDs, and Diverse Sources to find and amplify diverse expert voices.
Reach out to your State Climate Office or the nearest Land-Grant University to connect with scientists, educators, and extension staff in your local area.
METHODOLOGY
Average temperatures during Major League Baseball (MLB) season (March 30 – Oct 1) in each of the 27 MLB cities (representing 30 teams) were calculated for each year from 1970 through 2024 using data obtained from the Applied Climate Information System, which is developed, maintained, and operated by NOAA’s Regional Climate Centers. Temperature trends during the period of analysis (1970-2024) were calculated using linear regression.
During the 2025 MLB season, the Athletics are playing in Sacramento, Calif. while in transition from Oakland, Calif. to Las Vegas, Nev. This analysis therefore assessed temperature trends in Sacramento to determine warming trends for the Athletics.
Data on recent observed (2010-2019) and projected future effects of warming on MLB home runs are from Callahan et al. (2023). On the related graphic, projections for 20-year intervals (e.g., 2041-2060) are presented as a decadal midpoint (e.g., 2050s) for simplicity.
Based on Callahan et al. (2023), in climate model projections that assume global pledged commitments to reduce carbon pollution are met (SSP2-4.5), the average annual home runs added by climate change from 2050-2059 is 182. This represents a tripling of the recent observed rate of 58 home runs added by climate change annually from 2010-2019, and accounts for 3% of the average annual total home runs over this period (5,076).
By contrast, in climate model projections with very high levels of future carbon pollution and warming (SSP5-8.5), the average annual home runs added by climate change from 2090-2099 is 441, or a 9% increase over the 2010-2019 rate.