Since most tennis balls rely on their internal air pressure for their bounce, tennis players who want to increase the performance and longevity of their balls should consider how the temperature impacts their tennis balls.
When it comes to storage and adjustments in play, the air temperature can affect both the tennis player and the tennis ball.
How does temperature affect a tennis ball? Temperature affects a tennis ball by changing the internal pressure of the tennis ball. When it is hotter, the gas molecules inside expand and create higher pressure conditions in the ball, providing more bounce. When it is colder, there is less pressure internally and thus less bounce.
The Sweet Spot – 68 Degree Fahrenheit / 20 Degrees Celsius
Just like there’s a sweet spot on a tennis racket, there is a sweet spot when it comes to tennis ball temperature. Tennis ball manufacturers have established that 68 F/20 C is the best temperature to keep tennis balls. At these temperatures, the balls will retain their optimal pressure and bounce.
This is why big tournaments store their tennis balls inside fridges on the side of the court. Since the tournament organizers want to provide the best possible games between elite players, they want their competitors to use balls that are precisely calibrated.
A lot of smaller tournaments don’t do this, since supplying fridges for every court is a big expense, but you will see the pros cracking open a cold one—a cold tennis cannister, that is—in between matches.
Benefits of Keeping Your Tennis Balls at the Proper Temperature
Even if you’re not toting around a mini-fridge or a Yeti cooler to keep your tennis balls at 68 degrees, you can take some steps to keep them as close to 68 degrees as possible.
We’ll get into strategies on that in a bit, but first let’s answer the question of why you should care about the temperature, even if you’re not a pro.
If you play a lot, you’ll want to play with balls that are in the best possible condition and also increase the lifespan of your tennis balls so that you don’t have to keep buying new balls all the time. Taking note of the ball temperature is a great way to do that.
Pressurized tennis balls (the most common kind and the kind used in competition) rely on their internal air pressure. Without getting too deep into the science of how gas molecules work, the gist of it is this:
higher temperatures = more pressure in the ball, and lower temperatures = less pressure in the ball.
For a quick visual, grab a rubber band. Hold one end in your dominant hand and pull the other end back with your non-dominant hand as if you were going to flick it across the room.
Pull it back six inches and see how far it flies. Repeat the process, but this time pull it back 12 inches and see how much further it goes. By increasing the pressure on the rubber band, there is an increased energy output.
So if the tennis balls are at or around that optimal temperature, they’ll have the best amount of bounce, which will make them more fun to play with and more useful to simulate a competitive environment.
How To Store Tennis Balls
While you want to play at 68 degree, you can store tennis balls at lower than the optimal temperature to help increase their lifespan. If you don’t store your balls correctly, you’ll have to replace them more often, which is a pain when you want to play and a drain on your wallet.
As the temperature in and around the tennis balls rises, the gasses inside push against the rubber structure of the ball. Think of blowing a bubble with your chewing gum.
Eventually, if you keep blowing, the bubble will pop. While your tennis ball won’t likely explode, the gas inside will be pushing harder and thus seeping out at a higher rate. This means that your ball will die more quickly.
So even if you’re hitting the court every day, don’t leave your tennis balls in your car, especially in the spring and summer. The internal temperature of a car can be wildly higher than the temperature outside, which will cause massive gas expansion. The same goes for throwing your tennis bag into the garage—it’s not recommended.
Since garages don’t have the same amount of insulation as the rest of the house, they can get really hot. Not as hot as the trunk of the car, maybe, but hot enough to not be good for your tennis balls.
Instead, bring your bag inside your house or apartment and keep it in a cool, dark place. A closet or under the bed is a great place. Even if you don’t keep your AC set to 68 degrees, the temperature of your home is a lot closer to the optimal tennis ball temp.
If you’re really serious about getting the most out of your balls or you know that you won’t be playing for a while, toss the canisters in the fridge. In the United States, the Food and Drug Administration suggests that fridges are at or below 40 degrees Fahrenheit.
Since this is lower than the optimal temperature, you can prevent some of that gas seepage, since the gasses inside will be smaller and won’t press against the outside of the ball.
Playing conditions can heavily impact the way a tennis ball bounces. Sometimes when you show up to your court to play, the weather outside is colder than 68 degrees. Depending on where and when you play, it may be significantly colder than that. Unfortunately, this means your balls won’t bounce as much as you’re used to.
Luckily, if you know in advance that it’s going to be cold out, you can adjust your string tension. When the ball isn’t going to bounce as much, you’ll want more energy to come from your strings. Adjust them to about two pounds higher than your normal string tension.
Conversely, keep in mind that if you’re playing in very hot conditions, your balls will likely bounce much more than you’re used to. You could decrease your string tension and adjust your swing to make sure that your balls are still landing inside the lines.
In the 2018 US Open, the temperature on the court was more than 100 degrees Fahrenheit, which not only impacted the balls but the players and fans. If your match takes place in such conditions, keep in mind that there are going to be a multitude of factors impacting your game.
Remember that while you might feel like you’re melting, the tennis balls will soak up the sun and have much more zip on them.
What About Altitude?
It’s true that people living or playing at high altitudes have to make lots of adjustments due to being so far above sea level. And while it can feel a lot colder at higher altitudes, the thing that impacts the tennis balls at high altitudes is the air pressure.
If a ball is at 68 degrees at sea level and also 68 degrees at high altitude, they won’t bounce the same way. This is due to the lower air pressure at higher altitudes exerting less pressure on the ball. Luckily, they make high-altitude tennis balls, or local clubs at altitude can help you adjust your strings to compensate.
Keeping your tennis balls as close as possible to 68 degrees Fahrenheit is going to help them last longer and play better.
This means you should store them in your home or apartment, preferably in a closet or other shaded area. Cars and garages get too hot and will cause your tennis balls to lose their internal pressure much faster.
If you’re playing at below 68 degrees, know that the ball will bounce less. Try to adjust your string tension accordingly. If you’re playing in high temperatures, adjust your strings and swing to a much bouncier tennis ball.