We’ve reached the midpoint of the MLB season, and if it feels like the temperature at the ballpark has been particularly high this year, you might be onto something! Due to a number of factors, the 2025 MLB season may go down in history as its hottest ever. Let’s run through the five reasons why.
1. Athletics Move to Sacramento
Last season, the A’s played their final game at the Oakland Coliseum. This spring, they moved north to Sutter Health Park in Sacramento. Their new home differs from the Coliseum in many ways, and one change both players and fans have definitely noticed is that the games are a lot hotter. Sacramento is simply a hotter city than Oakland.
The Bay Area has a unique microclimate, with mild winters and cool summers. The warmest month on average is actually September. Sacramento, on the other hand, experiences more of a four-season climate. The average daily high in Sacramento in July is a full 20 degrees Fahrenheit hotter than in Oakland!
2. Rays Play Outdoors
The Rays joined MLB as an expansion franchise over 25 years ago and, during that time, only played outdoors during road series. Love it or hate it, Tropicana Field offers a climate-controlled indoor environment where the Rays never had to worry about heat, rain, or thunderstorms.
Unfortunately, in October 2024, Hurricane Milton caused substantial damage to the roof at Tropicana Field. Through no fault of their own, the Rays had to find a new home field fast. They struck an agreement with the Yankees to play at Steinbrenner Field, a venue primarily used for spring training and minor league games.
Matt May / Alamy Stock Photo
I’m sure Steinbrenner Field is a great place to catch a spring training game in February or March. Fans love flying down to Florida to take in a game on a warm, sunny day while snow covers the ground back home. However, it’s a different story in June, July, and August, when temperatures can easily exceed 90°F and the humidity is oppressive.
MLB has tried to mitigate the issue by concentrating the Rays’ home games at the beginning and end of the season, but there are still games scheduled in July and August. 2025 may be the only season the Rays play outdoors if the Trop is repaired soon, and if so, it will certainly be remembered as a hot one.
3. Earlier Evening Start Times
MLB team schedules include a mix of early afternoon, late afternoon and evening games. In pre-Covid times, these were typically around 1:00, 4:00, and 7:00 PM. Some teams started at incremental times like 1:35 or 4:05 or 7:15 PM but these were the three typical windows for baseball.
In recent years, MLB has made several changes to speed up games and make baseball more exciting. Many of the “pace of play” rules have worked, and games are notably faster than when they peaked in 2021.
Teams have also started moving up evening game times to make them more family-friendly and allow fans to see the entire game without staying out too late. Take the Washington Nationals, for example: in 2019 (the year they won the World Series), evening games started at 7:05 PM. With an average game length of 3 hours and 10 minutes, fans weren’t leaving the ballpark until around 10:15 PM.
In 2024, by contrast, Nationals games started at 6:45 PM, and the average game lasted 2 hours and 36 minutes. That means a full game wrapped up around 9:21 PM, nearly an hour earlier. That’s a big improvement for families bringing kids to the park or anyone who has work the next morning.
However, the downside is that earlier start times mean more of the game is played under the sun. Sunset in Washington, D.C., in June and July isn’t until after 8:30 PM, so more than half the game may be played before the sun goes down. And it’s not just the Nationals: in 2025, the Rockies have 37 home games at 6:40 PM, the Royals have 36 at 6:40 PM, and the Phillies have 32 at 6:45 PM, just to name a few.
4. Global Climate Trends
Last week, the United States experienced a major heat wave as a heat dome brought oppressive temperatures to many cities. On June 24, 2025, nearly every city hosting an MLB game experienced at least a minor heat advisory.
Global climate trends suggest we should expect more, longer and hotter heave waves. It doesn’t mean every game will be a scorcher, but it does mean we’ll likely see more games played in extreme heat more often, and earlier and later in the season than in years past.
5. Aging Ballpark Infrastructure
The Athletics and Rays have both moved to hotter ballparks this season, but not long ago the Texas Rangers went in the opposite direction. They transitioned from one of the hottest venues in baseball to a modern, climate-controlled stadium. If the A’s eventually move to Las Vegas, they could become the next team to play indoors.
The Arizona Diamondbacks already play indoors, but the climate control at Chase Field has struggled recently. Built nearly three decades ago, Chase Field was designed for a Phoenix that simply wasn’t as consistently hot as it is today. In 2023, Phoenix recorded a staggering 113 consecutive days of temperatures at or above 100°F. The HVAC systems at Chase Field are aging and unable to keep up with current demands. Even players have complained about warm, muggy conditions affecting their health and performance on the field.
Chase Field is scheduled to receive significant upgrades, including improvements to the HVAC system. But Houston and Miami, two other cities with retractable roof ballparks, are also seeing their stadiums age. Time will tell whether those venues experience the same issues as Phoenix has.