Can You Take Your Phone in a Sauna? What Heat Does to It

You can't safely take your phone into a sauna, and you shouldn't try. Apple designs iPhones to work in ambient temperatures between 0 and 35°C (Apple Support), Samsung quotes the same 32 to 95°F band for Galaxy phones (Samsung Support), and a traditional Finnish sauna runs at 70 to 100°C. That's double the upper limit, or worse. Apple's water resistance page goes further and names "using your iPhone in a sauna or steam room" as something to avoid outright (Apple Support). On top of the hardware risk, nearly every UK gym and spa bans phones in the hot room because people are sitting there in swimwear.

So the short answer is no. The longer answer depends on what kind of heat you're dealing with, because an infrared tent at home isn't the same as a 90°C spa sauna, and a steam room has its own problem.

Why sauna heat and phones don't mix

Phones are built around a lithium-ion battery, and heat is what ages those batteries fastest. Apple puts it bluntly: exposing a device to ambient temperatures above 35°C "can permanently damage battery capacity" (Apple batteries). The key word there is permanently. One session won't brick a phone, but a habit of scrolling through 15-minute rounds three times a week chips away at how long the battery lasts between charges, and you don't get that back.

There's also the case. A phone sitting on a wooden bench in 85°C air soaks up heat until the glass and aluminium are uncomfortable to hold. Dark cases and metal frames get there quicker. The phone has no fan; its only cooling trick is to slow itself down, and in a room hotter than its own internal limits that trick doesn't work for long.

What actually happens, in order

Apple lists the stages a hot iPhone goes through as it tries to regulate itself:

• Charging slows or stops.
• The display dims or goes black.
• Mobile signal weakens and some apps run slower.
• The camera flash may be disabled.
• A "needs to cool down" temperature warning appears and the phone becomes unusable until it cools.

Samsung describes much the same behaviour for Galaxy phones: they may power off, close apps, pause charging or dim the screen, with a "Device overheating" notice.

What neither company describes, but which is the real long-term worry, is battery swelling. A lithium-ion cell that's been cooked repeatedly can start to bulge, which pushes the screen away from the frame. If you ever notice your screen lifting or the back of the phone rocking on a table, stop using it and get the battery replaced.

Different saunas, different risks

Type	Typical air temperature	Humidity	Phone risk
Traditional Finnish sauna	70°C to 100°C	10 to 20%, spikes with water on the stones	High: far above the 35°C limit within minutes
Infrared cabin or tent	45°C to 65°C	Low	Moderate to high: above spec, and the emitters heat the phone directly
Steam room	40°C to 45°C	Close to 100%	High: moisture, not just heat
Sauna blanket	Liner set around 25°C to 80°C	Low	Moderate: the phone sits outside, but don't tuck it in with you

Those temperature ranges come from our sauna temperature guide.

Infrared saunas

People assume infrared is fine because the air feels gentler. It isn't fine; it's just less bad. A cabin at 55°C is still 20°C over what Apple and Samsung design for, and infrared panels warm whatever they're pointed at, not only the air. A phone on the bench facing an emitter can end up hotter than the room around it. If you've got a home cabin or tent and you want music, put the phone or a speaker outside the door and turn the volume up. Our infrared vs traditional sauna comparison explains why the two feel so different.

Steam rooms

Lower temperature, bigger problem. A steam room at 45°C is only 10°C over spec, but the air is saturated. Take a phone from a cool changing room into that and warm, wet vapour condenses straight onto the colder glass, around the buttons and into the charging port and speaker grilles. Apple lists "extremely humid conditions" alongside saunas and steam rooms as things to avoid.

An IP68 rating doesn't save you here. Those ratings come from controlled lab tests with still water, not hot vapour. Worse, Apple says liquid damage isn't covered under its warranty, so a dead phone after a steam room is your bill, not theirs. See sauna vs steam room for how the two compare more broadly.

Sauna blankets and portable tents at home

This is the one situation where having your phone nearby is reasonable, as long as it stays outside the heat. With a sauna blanket your head and arms are usually out, so propping the phone on a side table to watch something is fine. What isn't fine is zipping it inside the blanket with you or resting it on top of the heated liner. With a portable sauna tent, the steam versions usually leave your head outside, which makes a phone on a stand at face height workable. The infrared versions often enclose your head too, so the phone goes outside.

The etiquette problem

Even if your phone survived 90°C without complaint, you still couldn't use it in most public saunas. Gyms and spas ban phones mainly for privacy: everyone's in swimwear or towels, and a phone with a camera makes people uncomfortable whether you're filming or not. Calls and video audio break the quiet that most spa saunas expect. Our sauna etiquette guide covers the rest of the unwritten rules, but on phones it's simple: leave it in the locker.

Safer ways to time and soundtrack a session

Most people take a phone in for one of two reasons: to keep track of time or to play music. Both have better answers.

Timing. Many public saunas have a wall-mounted sand timer, often 15 minutes, which is a sensible maximum round for most people anyway. At home you can buy your own sand timer cheaply, or set an alarm on the phone and leave it outside the door. If you're not sure how long a round should be, our guide to how long you should stay in a sauna goes through it by sauna type and experience level. A phone also makes it far too easy to lose track of time, which is the last thing you want in that heat.

Music. Put a Bluetooth speaker outside the sauna door, or just inside a well-ventilated changing area, and stream to it from a phone that's also outside. Some dedicated sauna radios and speakers are built to sit inside the cabin with a stated heat rating; if you go down that route, check the manufacturer's maximum temperature against your sauna's actual reading rather than trusting the word "sauna" in the product name.

Home builds. If you're fitting a home sauna, it's worth planning a speaker mount or small window so you can see a timer outside. Our best home sauna guide covers cabins that make this easier.

What about smartwatches?

Smartwatches are a separate question because you're wearing them, and many people want heart rate data from a session. The manufacturer answers aren't encouraging.

Apple's guidance is the most specific we've found. It says to avoid wearing any Apple Watch in a steam room, to avoid wearing models other than Apple Watch Ultra in a sauna, and to avoid wearing an Ultra in a sauna above 55°C (Apple Support). Since a typical gym sauna is 75°C or more, that effectively rules out every Apple Watch, including the Apple Watch Ultra 3, for a proper Finnish session. An Ultra in a cooler infrared tent below 55°C is within Apple's stated limit.

Samsung's support page says Galaxy Watches show a heat warning at 113°F (45°C), then restrict calls, then power off automatically if they keep heating up. That's below the temperature of almost any sauna.

For Garmin, we couldn't find a sauna statement on Garmin's own support site that we could verify, so check the operating temperature listed in your specific model's manual before you wear it in. Whatever the brand, a water resistance rating like 5 ATM describes water pressure, not heat, and doesn't mean a watch is sauna-safe.

The verdict

Leave the phone outside. In a traditional sauna it's operating at double or more its rated limit within minutes, in a steam room the moisture is the bigger threat, and in an infrared cabin it's still well over spec. None of that damage is covered by warranty, and battery wear from heat is permanent. Use a sand timer or an alarm left outside the door, put the speaker out there too, and treat the sauna as the one place you're not reachable for 15 minutes.

Recommended reads

• Sauna etiquette: the unwritten rules
• How long should you stay in a sauna?
• Sauna temperature explained
• Best home sauna UK
• Portable sauna guide