Quick answer: No — and we'd gently suggest you shouldn't. Most smartphones are rated to a maximum of 35°C (95°F), while a traditional sauna runs anywhere between 70–100°C. That's a significant gap, and one your battery, screen, and internal components will feel. Bring a book instead. Your phone will thank you.
We've all done it. You're about to step into the sauna, you've got the perfect playlist lined up, and you think — just this once — you'll bring the phone in. Maybe you need the timer. Maybe you want to check in after 15 minutes. Maybe you just don't want to leave it unattended on a bench outside. If you use a sauna regularly, or you're weighing up whether to bring a phone, smartwatch, earbuds, or another device inside, this is the decision to make before you open the door.
We get it. But here's the thing: the sauna is genuinely one of the worst environments you can put a smartphone in. Heat, humidity, steam, and rapid temperature swings — it's essentially a hostile obstacle course for modern electronics, and the damage can be gradual, expensive, and irreversible. Below, we'll look at what sauna conditions do to phones, what to do if you absolutely must bring one in, better options for music and timing, and how the same risks apply to wearables and other electronics. Just as importantly, leaving your phone out of the sauna helps preserve the one thing the room is actually good at: switching off.
Will a sauna damage your phone?
Almost certainly over time, yes. A single short session might not write off your device immediately, but the damage is cumulative — and some of it can happen fast.
Heat damage and your phone's limits
Apple, Samsung, and Google all spec their flagship phones to a maximum operating temperature of around 35°C (95°F). A traditional Finnish sauna runs at 70–100°C. That's not a mild overshoot — it's more than double what your phone is designed to handle. Even an infrared sauna, which operates at cooler temperatures, still typically reaches 55–65°C. Both are well above a smartphone's threshold.
At elevated temperatures, your phone's processor starts throttling to protect itself, your screen can dim or go blank, and internal solder joints — the tiny connections holding everything together — expand and contract in ways they really weren't designed for. Phones are not built to operate in sauna conditions, and manufacturers usually treat resulting heat damage as user misuse that can void the warranty. You might not notice anything the first time. But the wear accumulates.
Lithium-ion batteries and high heat
This is the part worth paying attention to. Lithium-ion batteries (the kind in every modern smartphone) are particularly sensitive to heat, so a phone inside a hot sauna can start overheating quickly. Above 35°C, the internal chemical reactions start to accelerate beyond their intended pace, which degrades capacity over time. Push it further — into the territory of a hot sauna bench — and you risk battery swelling, which in extreme cases can warp your phone's casing, damage the screen from the inside out, and affect other internal parts.
Thermal runaway (where a battery's internal temperature spirals uncontrollably) is rare, but it's a real phenomenon, and sustained heat exposure is one of the conditions that increases the risk. We're not trying to alarm you — but a phone on a 90°C bench isn't a situation any manufacturer has designed for.
Moisture and steam: "water resistant" isn't the same as steam-proof
A lot of people assume that because their phone has an IP67 or IP68 rating, they're covered. They're not — at least not in a sauna.
Water resistance ratings relate to submersion in liquid water. They don't account for hot, humid air that seeps in through speaker grilles, charging ports, and microscopic gaps in the casing, and steam saunas can reach near-100% humidity. When warm sauna air with high humidity meets the cooler internals of your phone, condensation forms inside the device and leaves components wet. That trapped moisture then sits on your circuit boards, camera components, and connectors. Over time, it can lead to internal corrosion and the kind of slow-burning damage that shows up weeks later, not immediately.
Worth noting: the adhesive seals that give your phone its water resistance are also heat-sensitive. A few sauna sessions and those seals can soften and degrade, meaning your phone may actually become less water resistant the more you expose it to heat.
Rapid temperature changes
If you're doing the full recovery circuit — sauna, cold plunge, shower, repeat — your phone faces another risk: thermal shock. Moving a device rapidly between extremes of hot and cold causes its components to expand and contract quickly. This can crack internal solder joints and cause condensation to form inside sealed compartments. Not a great outcome for a device you rely on daily.
Phone in sauna safety: if you absolutely insist
We'd recommend leaving the phone out entirely. But if you genuinely need it nearby, here's how to minimise the damage:
- Keep sessions brief. Don't leave your phone in the sauna for a full 20-minute session. If you need it, check and leave.
- Keep it low and away from the heater. Heat rises, so the floor or the lowest bench is considerably cooler than head height. Never put it near the stones or the heater unit.
- Don't charge it in or near the sauna. Charging generates its own heat. Combining that with sauna temperatures is an efficient way to degrade your battery.
- Avoid steam directly on the device. If you're ladling water onto the stones, keep your phone well away.
- Use aeroplane mode. It reduces the heat generated by signal searching, and — bonus — it means fewer distractions.
- Respect the rules. If the sauna venue says no electronics, that's not a suggestion.
- If it feels hot to touch, take it out immediately and let it cool naturally at room temperature. Don't put it straight in a cold bag or under a cold tap.
Electronics in a sauna: smartwatches, earbuds, and Bluetooth speakers
Your phone isn't the only device at risk. Here's a quick rundown:
Smartwatches: The Apple Watch is rated to 35°C — the same as your iPhone. The straps can degrade with repeated heat exposure, and the seals aren't built for sustained sauna temperatures. Leaving it off during sessions is the safer habit.
Earbuds: Small lithium-ion batteries, near your head, in a moist, hot environment. Of all the electronics to bring in, earbuds are probably the highest-risk. Sweat and steam can enter the charging contacts, and the adhesives holding them together are particularly sensitive to sustained heat.
Bluetooth speakers: These are the exception. A decent waterproof speaker — ideally with an IPX7 rating or higher — can be placed near the sauna door or on the lower bench, away from direct heat. You can stream audio from your phone, which stays safely outside, so you can listen without exposing it to the heat. For entertainment, one of the safer alternatives is to keep the phone outside and use audio gear positioned outside or near the door. This is genuinely the best of both worlds if music matters to you.
Better alternatives for music, timing, and that one urgent notification
The honest answer is that most of what we bring our phones in for can be sorted without them, while preserving the benefits of the sauna without risking the phone:
- Timer: A simple sand hourglass or analogue clock kept in the cooler part of the sauna works perfectly. Many saunas have built-in timers — use them.
- Music: Set your playlist before you go in, pair a waterproof Bluetooth speaker, and leave the phone outside. Problem solved.
- Notifications: If 15–20 minutes offline is genuinely a crisis, leave your phone just outside the sauna door. You'll hear it if something urgent comes through.
- Mindfulness: Not a feature, we know — but the sauna is one of the few places left that naturally encourages you to spend a short time offline, relax, unwind, and breathe, which supports real relaxation. That's not a design flaw. It's part of why it works.
Frequently asked questions
Can you take your phone in a sauna if it has a water resistance rating?
No — water resistance isn't the same as heat or steam resistance. IP67/IP68 ratings cover submersion in liquid water, not hot, humid air. The seals and adhesives that provide that protection are also heat-sensitive and can degrade in sauna conditions.
Will a sauna damage your phone straight away?
Probably not after a single brief session. But the damage is cumulative. Battery capacity degrades, solder joints weaken, and moisture works its way into components over time. Most problems appear gradually, which makes it easy to underestimate the risk.
Is it safer to bring your phone into an infrared or dry sauna?
Somewhat — infrared saunas run cooler (typically 55–65°C) than traditional Finnish saunas (70–100°C), so the type does matter slightly for how severe the risk is. But neither is safe for a phone, and even a dry sauna still far exceeds your phone's maximum operating temperature of 35°C. The same heat and moisture risks apply; they're just slightly less acute.
What's the safest way to use your phone as a timer during a sauna session?
Set a timer on your phone before you enter, then leave it outside the sauna room door. You'll hear it go off without ever needing to bring the device inside. Alternatively, use the sauna's built-in timer or a simple analogue option, or store your phone in a locker when one is available — no electronics required.
Can I bring my smartwatch into the sauna?
Most major smartwatches, including the Apple Watch, are rated to 35°C — the same limit as your smartphone. While many users wear them without immediate issues, repeated exposure degrades battery life and seals over time. Leaving it off during sessions is the safer long-term habit.
A quick word from us at Vitru: the sauna is for switching off
We know recovery takes discipline. Showing up consistently, doing the sessions, not skipping the cold plunge because it's cold. But part of what makes regular sauna use so effective — for stress, for sleep, for that general sense of having done something genuinely good for yourself — is the enforced disconnection.
The sauna has been a place for quiet reflection long before smartphones existed, and that hasn't changed. Some of our customers tell us it's the only part of their day where they properly switch off. We think that's worth protecting.
Keep the phone outside. Sweat properly. You can check your messages after.
If you're building a sauna routine that actually helps you switch off — and keeps your phone safely on the sidelines — have a look at our sauna range, built for serious recovery and consistent, proper heat. Explore our saunas here.