Anyone who has left their cell phone in the sun on a hot day has experienced how heat can affect batteries: your phone itself may get extremely hot, or even just shut itself down. Cell phones use lithium-ion batteries, which don’t fare well in high temps. And there’s another device with lithium-ion batteries that may be affected by extreme temperatures: your EV.

Electric vehicle adoption is seen as a way to curb the amount of transportation emissions we send into the atmosphere that warm the planet. But in our already-getting-hotter world, EVs may be also be affected themselves by high temperatures. As heat waves continue across the country, places like Southern California and Texas are seeing triple-digit temperatures—conditions that could prematurely age your EV battery.

“Once it gets above 85 degrees, lithium-ion batteries do see accelerated aging and degradation,” says Liz Najman, lead researcher at Recurrent, a startup that provides EV battery reports for used cars. “It’s definitely a concern, and something a lot of EV makers have thought about.” Most EV manufacturers now have thermal management systems in place to keep their batteries in a healthy temperature range, Najman adds, but depending on the manufacturer, that system may only kick in when the vehicle is plugged in or on.

Chemical reactions are happening in EV batteries all the time, even when they’re not in use. And those chemical reactions happen more quickly at higher temperatures. “That goes for both chemical reactions that you want to happen in a battery—the things that make the car go—but that’s also true of some secondary chemical reactions that happen in the battery that cause your baseline aging,” Najman says.

Think about it the way smoking affects humans: “You’re aging all the time, and if you smoke cigarettes, you age faster. It’s pretty much the same in batteries: adding heat to that equation accelerates all of the aging processes,” says Najman. “It’s like your car is smoking cigarettes, or going to a tanning bed.”

Your electric vehicle almost certainly won’t just completely shut down in extreme heat like a phone might, and though you may see some short-term effect on range, the real concern is long-term battery health (extremely cold temperatures are more likely to cause an immediate, intense effect on your range). If your EV is sitting around in extreme heat, it could lead to faster aging that reduces the battery life span.

Depending on where you live, you may also recieve a notice to limit EV charging during heat waves. That comes from concerns about the power grid, and shifting charging times to off peak hours so as not to overload the grid while everyone has their air conditioning on and businesses are still open.

But it’s not a terrible idea to avoid charging your car in the middle of a hot day for battery longevity reasons either, Najman adds. Not only is off-peak electricity likely cheaper, but charging your EV is another thing that speeds up those chemical reactions, particularly fast charging. The combination of fast charging and high temperatures accelerates battery aging even further.

For EV owners, Najman recommends limiting how often you use a fast charger when it’s really hot out. “If you’re going to fast charge, try to do it when you haven’t just been on the highway for two hours and your battery is going to be a little cooler,” she says.

And if you have to leave your EV in the sun or in the heat (if you don’t have an air conditioned garage, for example), try to leave it more in the middle of the charge range; you don’t want it fully charged, or fully discharged. That’s because inside a fully charged or completely empty EV battery, the energy balance is skewed to one extreme; closer to the middle, she says, is where batteries are more chemically stable.

Though you don’t want to leave your EV charging during a hot day, you may need to have it plugged in to kick on that internal thermal management system. This varies by manufacturer; some electric vehicle thermal management systems are on all the time, while for others the car needs to be plugged in. “If you live somewhere where it’s really hot, you just may want to keep your car plugged into your home charger with a charge limit of 80%,” Najman says.

Recurrent is still working to learn what happens to EV batteries in extreme heat. Most scientific experiments are done on individual battery cells in a lab, but things may change in real world circumstances. Some manufacturers including Tesla and GM are also looking into lithium iron phosphate EV batteries, which tend to hold up better in heat (though they’re still batteries, Najman notes, and will still degrade faster than normal in extremely hot conditions). Lithium iron phosphate batteries may be slightly less energy efficient than lithium-ion batteries, but they’ll likely degrade at a slower rate and hold up better to fast charging.

Ultimately, if you need to drive long distances, stop at a fast charger on a hot day, or can’t park your EV in the shade or a cool garage, it’s not the end of the world, though it won’t be great for your battery if you do it a lot over the long term. “These are general recommendations for maintaining battery health,” Najman says.