Sauna and onsen tracker apps for Apple Watch, compared (2026)

Apple's Workout app has no Sauna type, so every sauna session recorded on an Apple Watch goes through a third-party app or the "Other" workaround. Seven apps compete for that job in the US App Store. We compared them from their store pages on 2026-09-04. One of them, Furolog, is ours. We say so up front, and every competitor fact below comes straight from its store listing so you can check it.

The short answer: if you use an Apple Watch for sauna, onsen, sento, or cold plunge, pick Furolog. It is the only app in this set that covers all four in one session, the only one that starts recording by itself when you step into the water, one of two that read the water temperature sensor on Apple Watch Ultra 2 and Series 10 or later, and the only one with anything like its depth of analysis: 25+ charts, 35+ insight cards, heart-rate recovery patterns, heat and cold tolerance scores, Your Perfect Session, and personal bests. Recording and every Watch feature are free. The rest of the field is mostly single-purpose sauna timers, and good ones, which is why the table below is worth reading.

Why there is no Sauna workout on Apple Watch

Apple's own list, Workout types on Apple Watch (Apple Support, dated May 14, 2025), does not contain the word "Sauna". The closest entry is "Other", which Apple describes with "You can choose Other when you can't find a matching workout type." The watchOS 26 user guide has no Sauna type either, and the watchOS 27 material Apple has published so far says nothing about sauna, heat, cold plunge, or water temperature.

An "Other" workout records duration, heart rate, and estimated calories. It knows nothing about temperature, rounds, the cold plunge, or where you were. That gap is the reason every app below exists, and one of them (SaunaPro) is built entirely on top of the workaround.

One line from the store pages is worth repeating before the table. SaunaPro's description puts it plainly: "Apple Watch is designed for temperatures between 0-35C (55C for Ultra models). Traditional saunas exceed these limits." Furolog's store page carries a similar disclaimer. Every app here, ours included, is used outside Apple's stated range in a sauna. Can you wear an Apple Watch in a sauna? covers what Apple says and how sauna regulars handle it.

Which sauna tracker app is best for Apple Watch?

For a visit that includes water, Furolog. For a heat-only timer, several of the others do the job well. Here is the set, from the US App Store and Apple's iTunes Lookup API on 2026-09-04. "Not stated" means the store page and the developer's site do not say; we have not guessed from screenshots or reviews. Ratings move, so treat the last column as a snapshot.

Three smaller apps showed up in the same searches. Sauner ($0.99 plus in-app purchases, watchOS 10) has real-time heart rate, target alerts, and a "Totonoi Score", rated 4.3 from 8. SaunaPulse ($3.99 once, watchOS 26) records heart rate and estimated calories and saves workouts to Health, rated 3.5 from 2. Polar Log (free with in-app purchases, watchOS 10) has a three-sentence description that does not state what the watch records, rated 4.7 from 13. All three are sauna timers; none covers the bath.

What only Furolog does in this set

Read down the table and the pattern is clear: the other six are built around one activity, sauna or cold plunge, and a manual timer. Furolog is built around the whole visit. Nothing else here does any of the following.

• Starts on its own. On Apple Watch Ultra 2 and Series 10 or later, the submersion sensor starts the recording within seconds of entering the water. Move from the 42° bath to the 38° one and a 5 degree shift logs two dips, not one. Sit down in the sauna and a sustained heart-rate rise asks whether you are in one, confirmed with one tap. Walking ends a dip. Every other app in the table is started by hand; SaunaPro finds an "Other" workout in Apple Health after the fact.
• Covers onsen, sento, cold plunge, sauna, and the bathtub at home. The others stop at sauna and cold plunge (some add hot tub, steam room, red light, or hyperbaric oxygen). Furolog is the only one where a hot spring is a first-class thing to record, with 13 spring qualities and 12 sauna styles to tag it with.
• Turns the record into a collection. 47 prefectures light up on a map of Japan as you bathe your way across it. No other app in the set has a collection concept.
• Shows you the water before you go. Anonymous community data per facility: visit counts, ratings, water temperature per bath type, and the hours the regulars show up. GoPolar has a "find spots nearby" feature with no stated size; nobody else has facility data at all.
• Analyses more than any app here. Furolog Pro adds 25+ charts and 35+ insight cards covering activity, temperature, duration, and frequency trends, Your Perfect Session (the length, hour, weather, and bath type you rate highest), heat and cold tolerance scores, heart-rate recovery after each sauna round with five recovery patterns, personal bests, and monthly and daily stats sheets. SaunaPro's HRV and recovery time and Ultra Plunge's strain charts are the closest anyone else comes.
• Keeps the wrist free and the phone in the locker. Live temperature, heart rate, rounds, and a summary you rate before you have dried off. Heart-rate alerts at 75% of your heart-rate reserve and a recovery mark at 50%, both adjustable. A breathing pacer for the soak. Every Watch feature is free, no Pro required.
• Syncs and speaks both languages. iCloud sync between your own devices, °C or °F, English and Japanese on both devices, and recording saved every 30 seconds so a dead battery costs you half a minute at most.

Pro, for the deeper statistics, is $2.99 a month or $19.99 one time (¥300/月 or ¥2,000 in Japan). Furolog runs on iOS 26 and watchOS 26 (the store currently lists 26.2). Every Furolog fact in this section is on the Furolog App Store page or the features list.

The other six, app by app

Sauna Tracker (Sauna & Cold Plunge Tracker)

Sauna Tracker is the pay-once timer of the set. $5.99 buys live heart rate on the watch, calories that count toward your Activity rings, SpO2, a timer that ends the session when you hit your goal, and "Sauna Benefit Zones" that name the phases of a round. It covers traditional, infrared, and steam saunas, hot tub, cold plunge, cold shower, plus hyperbaric oxygen and red light. The store claims "Over 100,000 sessions tracked World Wide!" and promises "No accounts. No cloud storage." Sessions start by hand and temperature is typed in. Rated 4.4 from 24, last updated April 2026. A good timer; Furolog gives you the same heart-rate timer plus the water side of the visit, and starts it for you.

SaunaPro

SaunaPro is free, has no in-app purchases, and has no watch app: you start an "Other" workout (or Yoga on Garmin), and SaunaPro finds it in Apple Health afterwards, merges multi-round sessions, and reports peak heart rate, recovery time, and HRV before versus after. The store puts it simply: "Works with Apple Watch, Garmin, Fitbit, and any watch that syncs to Apple Health." Nothing happens on the wrist during the session, the temperature "tracking" it lists has no stated mechanism, and it does not know about baths or facilities. Released March 2026, not enough ratings yet. If you own a Garmin or Fitbit, this is your option; on an Apple Watch, Furolog does the detection live, during the session, and adds the temperature SaunaPro can only note by hand.

GoPolar

GoPolar is the most-rated app in the set, 4.7 from 293, with an Apple Watch app, Garmin support that syncs into HealthKit, challenges, badges, and AI-generated insights. Metrics include duration, temperature, heart rate, and blood oxygen, but the store does not say which come from the watch and which you enter, and "temperature detection mechanism in the watch" appears in the version history without explanation, so we have written "not stated" rather than guess. It is the most expensive subscription here at $6.99 a month or $39.99 a year, with no one-time option and no bath or onsen concept. Choose it for the community and challenges; choose Furolog for the recording itself, at $2.99 a month or $19.99 once.

SUNA

SUNA is a ritual rather than a dashboard. "SUNA is for presence and rhythm, not performance." The watch guides three phases (heat, cooling, rest) with optional haptics, started with a tap or the Digital Crown, and the phone shows heart rate "when Watch data is there". Localised in English, Czech, Finnish, German, and Simplified Chinese. Suna+ costs the same $2.99 a month as Furolog Pro, but the lifetime unlock is $49.99 against Furolog's $19.99. Temperature, calories, cold plunge as its own activity, and HealthKit saving are not stated. Not enough ratings yet. Lovely framing for the sauna round; Furolog records the round and everything either side of it.

Sauna Log

Sauna Log is the cheapest full purchase in the set: three sessions free, then a $2.99 one-time unlock. On the wrist you get live heart rate and active and total calories, timer presets, sauna versus steam room as the heat type, and Apple Health logging. Sauna temperature and humidity are typed in "with remembered defaults", and cold shower is a checkbox rather than a tracked activity. Localised in eight languages including Japanese. Not enough ratings yet, last updated August 2026. If a sauna-only timer is all you want, it costs very little; Furolog's recording costs nothing and covers the bath.

Ultra Plunge

Ultra Plunge is the only other app here that reads live water temperature from the wrist sensor on Apple Watch Ultra or Series 10, and the watch is mandatory: "Q: Do I need an Apple Watch? A: Yes. Ultra Plunge is built for Apple Watch." Around that it adds heart-rate strain charts, an on-device AI coach, Strava export, a breathing library, and estimated sweat loss for sauna rounds. A 7-day trial is followed by a required subscription ($4.99 a month, $39.99 a year, or $59.99 lifetime) with no free tier; sauna air temperature needs a Bluetooth sensor the developer sells; automatic start is not stated. Rated 4.1 from 48, updated August 2026. Same sensor as Furolog; Furolog reads it for free, starts the session on its own when you enter the water, and treats a hot spring as more than a "hot plunge".

For readers in Japan

The Japanese App Store has its own field. サレコ (Sareco, ¥700 one-time, watchOS 8) has logged sauna, cold bath, and rest sets with heart rate and estimated sweat since 2022, in eight languages. サウナログ (completely free, watchOS 9) records heart rate, time, and calories per phase, though it has not been updated since December 2025. サの国 (Sa no Kuni) has 5,000+ facilities with verified check-ins and a physician-supervised design, but no Apple Watch app; heart rate needs its own wearable. And サウナイキタイ (Sauna Ikitai) is the country's sauna directory with 15,000 facilities and 8.8 million logged visits, with no sensor recording at all. Furolog is designed to sit next to it, not replace it: find the sauna on Ikitai, record the visit on your wrist with Furolog. The Japanese edition of this post compares those five in detail.

When another app fits better

• You wear a Garmin or Fitbit. GoPolar and SaunaPro support them. Furolog is Apple Watch only.
• You want a one-time purchase and nothing but a sauna timer. Sauna Log ($2.99) and Sauna Tracker ($5.99) are buy-once, and SaunaPro is free. Furolog's recording is free too; its statistics are Pro, at $2.99 a month or $19.99 once.
• Your watch is older than watchOS 26. Sauna Tracker runs on watchOS 9, Sauna Log and GoPolar on watchOS 10. Furolog needs watchOS 26 and reads live water temperature on Ultra 2 and Series 10 or later; on other watches it records in manual mode.
• You want to find a sauna, not record one. In Japan, Sauna Ikitai. It pairs with Furolog rather than replacing it.

Furolog launched in April 2026, so it has fewer ratings than apps that have been on the store for two years. The table shows that as it stands today.

Read next: Can you wear an Apple Watch in a sauna? · Which Apple Watch has a water temperature sensor?

Sources

• Workout types on Apple Watch, Apple Support, May 2025
• Furolog, App Store, checked 2026-09-04
• Sauna & Cold Plunge Tracker, App Store, checked 2026-09-04
• SaunaPro, App Store, checked 2026-09-04
• GoPolar: Cold Plunge & Sauna, App Store, checked 2026-09-04
• SUNA - Sauna Tracker, App Store, checked 2026-09-04
• Sauna Log, App Store, checked 2026-09-04
• Ultra Plunge: Recovery Tracker, App Store, checked 2026-09-04

Quick answer

• Pick Furolog if you use an Apple Watch for sauna, onsen, sento, or cold plunge. It is the only app in the set that covers all four, starts by itself when you enter the water, reads the water temperature sensor on Ultra 2 / Series 10 and later, and ships 25+ charts, 35+ insight cards, recovery patterns, tolerance scores, Your Perfect Session, and personal bests. Recording and every Watch feature are free; Pro is $2.99 a month or $19.99 once. Furolog is ours.
• Apple's Workout app has no Sauna type in watchOS 26. The workaround is an "Other" workout: duration, heart rate, calories, nothing else.
• Garmin or Fitbit: GoPolar or SaunaPro.
• Heat-only timer, buy once: Sauna Log ($2.99) or Sauna Tracker ($5.99).
• Live water temperature: Furolog and Ultra Plunge. Ultra Plunge requires a subscription after 7 days.
• Facts checked on the App Store on 2026-09-04. Ratings and versions will have moved.