Hot Onsen in Kyushu: Where to Find a 45°C Bath
Find published 42°C and 45°C pools at Cosmos Onsen, hot-and-warm labels in Beppu, and why Obama’s 105°C figure is source temperature.
Kyushu’s hot-spring figures describe either source water or the bath itself. A 105°C source is cooled before bathing, while a bath labelled “hot” has no exact temperature published. The examples below distinguish measured pool temperatures from local descriptions and source-water readings.
| Place | What is documented | Good fit | Check before you go |
|---|---|---|---|
| Cosmos Onsen, Kobayashi | The regional onsen listing gives a 42°C warm bath and a 45°C hot bath | Travellers specifically seeking a very hot pool | The city page lists public hours and prices, but a January 2026 visitor report says non-Miyazaki residents were turned away; call first |
| Beppu municipal baths | Some facilities have clearly labelled hot and warm pools, without publishing fixed temperatures | A first hot-bath attempt with a nearby alternative | Temperature can vary; do not assume that “hot” always means one Celsius figure |
| Takeo Onsen Motoyu | The current official listing confirms a historic public bath and its operating details; it does not promise a fixed pool temperature | A traditional bathhouse where a hot/warm contrast may be present | Do not plan around a permanent 45°C setting |
| Lamune Onsen, Nagayu | The operator lists a 42°C indoor bath and a 32°C outdoor bath | A moderate hot bath with a cooler alternative at the same facility | The lower-temperature outdoor pool is not the same as the indoor bath |
| Obama Onsen | The association lists a source temperature of 105°C | Seeing steam and understanding a high-temperature source area | 105°C is not a bathing-pool reading |
Cosmos Onsen: the clearest published 45°C pool
The Kyushu Onsen Program’s current facility page lists two pools at Cosmos Onsen in Kobayashi: a 42°C “warm” bath and a 45°C “hot” bath, both supplied by a 100% free-flowing hot source. Kobayashi City’s May 2026 directory lists the facility at ¥500 for adults, open 10 a.m.–9 p.m., and closed on Thursdays.
A visitor note dated January 8, 2026, says non-Miyazaki residents were turned away on that visit. The city directory gives no residency rule, so current access for visitors from outside the prefecture is unconfirmed. Call 0984-22-7085 before making the detour; choose another bath if the facility cannot confirm entry.
Cosmos Onsen is not beside JR Kobayashi Station: the regional listing estimates a 12-minute taxi ride, while Kobayashi City lists the bath’s address and contact information. It fits better into a local drive than a tight rail transfer. Its 45°C pool is a real published bathing temperature, not a source-water number—but do not treat the temperature as an endurance challenge.
Beppu: hot-bath culture without a precise thermometer claim
Beppu City says its waters tend to be hotter than those in other prefectures and notes that some municipal baths offer pools labelled “hot” and “warm.” That is useful for choosing a pool by feel, but the city does not publish a guaranteed Celsius figure for every hot bath.
The station-area public baths make Beppu a flexible choice: if the hotter pool feels like too much, you can use the warm pool or choose another bath nearby. Check the city’s current closure calendar before heading out. See the Beppu municipal-bath guide and station-area comparison for locations and current practical details.
Takeo Motoyu: admission, hours and temperature
Takeo Onsen Motoyu is described by the local tourism association as Japan’s oldest wooden public bathhouse still in use. Adult admission is ¥500; it opens from 6:30 a.m. to 11:45 p.m., with last reception at 11 p.m. A fixed pool temperature is unconfirmed.
A visitor entry dated June 17, 2026, on the Kyushu Onsen Program page described the pools as roughly 45°C and 42°C that day. That is a dated observation, not a promise for every season or visit. If you are going because you want a specific temperature, call Motoyu first and check the official listing below for current admission and access details.
Lamune Onsen: a 42°C bath with a cooler pool beside it
Lamune Onsen in Nagayu lists its indoor bath at 42°C and its outdoor bath at 32°C. Both are natural spring water; the useful distinction for a hot-bath visitor is the temperature range available at one facility. You can choose the indoor pool without committing to a 45°C bath, while the cooler outdoor pool is there if you prefer a lower temperature.
The operator lists adult admission at ¥800, opening from 10 a.m. to 10 p.m. and a regular closure on the first Wednesday of the month, moving to the second Wednesday in January and May. This is a convenient option when you want a clearly published pair of temperatures, though Nagayu is a destination in its own right rather than a station-side stop. Read the Nagayu day-use comparison before planning several baths in the area.
What Obama’s 105°C figure actually tells you
Obama Onsen’s ryokan association lists its source temperature as 105°C. That describes water at the source, not the temperature of an outdoor bath, public bath or hotel pool. Operators bring source water to bathing conditions in different ways, so there is no sound basis for ranking an individual bath at 105°C unless that bath itself publishes such a measurement.
The same distinction applies elsewhere: source analysis, temperature at the pipe and temperature in the bathing pool are different measurements. For background, see how to read onsen water temperatures. If the goal is to visit hot springs that feel hot rather than to see a hot source, choose a facility with a published pool temperature or an explicitly labelled hot bath.
Take high heat seriously
Japan’s Ministry of the Environment advises older adults and people with high blood pressure, heart disease or a history of stroke to avoid bathing at 42°C or above. Its onsen guidance also recommends allowing the body to adjust with a shower before entering, avoiding baths after alcohol or heavy fatigue, and taking care around hot water. This is general guidance, not an individual medical assessment. If bathing is restricted for you, follow your clinician’s advice and the facility’s notices.
For a 42–45°C day, make one hot bath the main activity. Do not add several hotter pools just to compare them. If you start to feel dizzy or unwell, leave the pool and rest; if you are simply looking for a longer, gentler soak, choose a lower-temperature option instead. The Kyushu two-bath itinerary explains how to leave a proper break between visits.
Sources
- Kobayashi City: [Hot springs and bathing facilities](https://www.city.kobayashi.lg.jp/kanko_bunka_sports/kankojoho/asobu_miru/3130.html) — Cosmos Onsen address, phone, hours, weekly closure and admission, updated May 8, 2026. - Kyushu Onsen Program: [Cosmos Onsen](https://www.88onsen.com/spot/detail/hid/135) — published 42°C/45°C pool temperatures, free-flow information and an entry posted January 8, 2026 noting an admission restriction experienced by a non-Miyazaki resident; the rule should be verified with the operator. - Beppu City: [Frequently asked questions](https://www.city.beppu.oita.jp/sangyou/onsen/faq.html) — hot/warm public-bath labels and local temperature context. - Takeo Tourism Association: [Takeo Onsen Motoyu](https://www.takeo-kk.net/spa/001331.php) and Kyushu Onsen Program: [Motoyu](https://www.88onsen.com/spot/detail/hid/11) — current admission and hours; the latter includes a dated June 17, 2026 visitor temperature observation. - Lamune Onsen: [Facility information and fees](https://lamune-onsen.co.jp/access/) — 42°C indoor bath, 32°C outdoor bath, admission and hours. - Obama Onsen Ryokan Association: [About Obama Onsen](https://obama.or.jp/onsen/) — 105°C source-water temperature. - Ministry of the Environment: [Precautions for bathing in hot springs](https://www.env.go.jp/nature/onsen/docs/kyokucho.pdf) — general hot-bath precautions, including guidance for people with certain health conditions.Tags: Kyushu onsen, hot onsen Japan, 45 degree onsen, hot bath Kyushu, Kobayashi Cosmos Onsen, Beppu public baths, Takeo Onsen Motoyu, Nagayu Onsen, Lamune Onsen, Obama Onsen, onsen bath temperature, hot spring source temperature, hot water bath, onsen safety, Japan hot springs
