IRONMAN Switzerland Thun
Thun, Switzerland · July · IRONMAN
Why people love it
- Alpine lake swim with a postcard Niesen backdrop
- Smooth, closed roads and a very scenic Bernese Oberland bike
- Flat, loud three-lap run through Thun (79-120 m (259–394 ft) / 260-390 ft of gain)
- Reports praise the organisation; course record of 7:49:20 in 2025
Watch out for
- Lake water of about 16-18 °C (61-64 °F)
- Hilly bike (about 1,900-2,200 m (6,230–7,220 ft) / 6,250-7,220 ft) with technical descents and about 52 turns per lap
- Very hot days possible (2023: up to 36 °C (97 °F) / 97 °F)
- Lodging is scarce and very expensive; Spiez or Interlaken as fallbacks
- Few personal blog reports exist for Thun editions
Race
How racers feel about it, how well it is run, and how it treats a first timer. Counts for 27% of the overall score.
- Racer satisfactionLoved4.4
Forum posts glow about scenery, pavement and organisation, calling it among the best IM races on the planet. Cost, heat and hills count against it. · Medium confidence
- OrganizationWell run4.4
A 2022 finisher called it the best-organised IRONMAN he had raced. 2023 heat caused heavy attrition, and 7 of 30 pro men DNF'd in 2025. · Medium confidence
- First timer friendlyDoable2.6
A cool lake, a hilly bike with technical descents and high costs make it a poor first-full pick, though organisation and closed roads help. · Medium confidence
Course traits, not part of the score
- PR potentialAverage2.8
About 1,900-2,200 m (6,250-7,220 ft) of bike climbing makes a PB harder than at flat races, though the 2025 course record is 7:49:20. · Medium confidence
- Course easeVery tough2.4
A hilly two-loop bike with 12%+ ramps and a technical 8 km (5 mi) descent, plus 2023 heat up to 36 °C (97 °F). · Medium confidence
Swim
Wetsuit odds, water temperature, calm, and the experience of the start. Counts for 15% of the overall score.
- Wetsuit legalAlmost always4.8
Water is typically 16-18 °C (61-64 °F), far below the 24.5 °C (76.1 °F) limit, so wetsuits are essentially always legal in early July. · Medium confidence
- Water temperatureAcceptable3.3
At 16-18 °C (61-64 °F) a wetsuit makes it comfortable, but 2024 was about 16 °C (61 °F). · Medium confidence
- Calm waterMostly calm3.7
A sheltered alpine lake, calm and misty most years. 2023 was choppy and 2024 had a slight swell. · Medium confidence
- Swim easeEasy3.6
A single-loop rolling start with a congested canal and harbour exit. Some 2023 athletes logged about 4.1 km (2.5 mi). · Medium confidence
- Swim experienceGreat4.4
A clear alpine lake, a postcard Niesen backdrop and a rolling start. The crowded exit is the one blemish. · Medium confidence
Bike
Road surface, closures, scenery and wind. Counts for 19% of the overall score.
- Road surfaceSmooth tarmac4.8
Swiss roads are maintained annually, and reviewers call the pavement excellent. · High confidence
- Road closuresFully closed4.6
Forum posters cite closed bike roads, and we found no safety complaints. · Medium confidence
- Bike scenerySpectacular4.8
The Bernese Oberland with an Alps backdrop. Reviewers call it among the most beautiful courses. · High confidence
- WindMostly calm3.6
A headwind on the second loop was noted in 2022. We found no systematic wind complaints in the Alpine valley. · Low confidence
Course traits, not part of the score
- Bike speedAverage3.1
Smooth roads and long descents offset about 2,000 m (6,560 ft) of climbing and about 52 turns per lap. Age-group splits of 5:30-6:00+ are typical. · Medium confidence
- Bike flatnessRolling2.5
Sources give 1,906 m (6,253 ft) to about 2,200 m (7,220 ft) over two loops. Reviewers say it is not as hard as you think. · Medium confidence
- Bike simplicityTechnical2.4
About 52 turns per lap, double hairpins, an 8 km (5 mi) technical descent and no-aero zones. One rider nearly skidded in 2023. · Medium confidence
Run
Crowds, aid stations, conditions underfoot and scenery. Counts for 13% of the overall score.
- Crowd supportStrong4.3
2022 reports call the crowds incredible through the course, with about 50,000 spectators expected and a loud swim exit. · Medium confidence
- Aid stationsGood4.1
Reports praise the aid stations, with Coke, soup and salt available in the 2022 and 2023 heat. · Medium confidence
- Run sceneryBeautiful4.1
Lakeshore, Schadau park, a historic bridge and the old town. · Medium confidence
- Run conditionsModerate3.4
Flat, but three laps on mixed surfaces (tarmac, gravel, cobbles, athletics track), and heat can bite (26 °C (79 °F) / 79 °F in 2022). · Medium confidence
Course traits, not part of the score
- Run flatnessFlat4.5
About 79-120 m (260-390 ft) of gain over three flat laps through town and the lakeside. · Medium confidence
Conditions
Air temperature, how predictable the weather is, setting, and spectating. Counts for 15% of the overall score.
- Air temperaturePleasant3.5
Air ranges 15-30 °C (59-86 °F), mostly comfortable. The 2023 heat wave reached 36 °C (97 °F) on the bike. · Medium confidence
- Weather reliabilityVariable3.1
Alpine summer weather: a heat wave in 2023, misty cool mornings in 2022 and 2024, and possible thunderstorms. We found no cancellations. · Low confidence
- Venue beautyStunning4.8
Lake Thun with an Alps backdrop, widely called spectacular. · High confidence
- Spectator friendlyEasy4.1
A village at the finish area, run laps through town, a bike course that passes near the start and good train access. · Medium confidence
Course traits, not part of the score
- Low altitudeModerate3.3
Thun sits at about 560 m (1,840 ft). · High confidence
Stay and travel
Hotels, walkability, getting there, and the town around the race. Counts for 11% of the overall score.
- Hotel availabilitySells out early2.1
Posters struggle to find lodging near the venue, with Spiez (10 minutes by train) and Interlaken (45 minutes) as fallbacks. · Medium confidence
- Hotel valuePricey1.5
Posters cite about 600 per night for a one-bedroom and say costs deter athletes, with a strong Swiss franc. · Medium confidence
- WalkabilityWalkable3.5
The Seepark hotel is about 1 km (0.6 mi) from finish and expo. A shuttle runs from Panorama-Center parking; otherwise walk 2 km (1.2 mi). · Medium confidence
- Travel easeEasy3.9
An excellent train network. Bern airport is about 25 km (16 mi) away; Zurich flights then train also work. Bike rental can be hard. · Medium confidence
- LogisticsSimple3.5
Registration and bike check-in are the day before, with shuttles and parking arranged. The transition layout is undocumented. · Low confidence
- Town and foodGood4.1
Thun old town and lakeside restaurants, though prices are high. · Low confidence
Key facts
- Location
- Thun, Bern, Switzerland
- Typical month
- July
- Latest or next date
- 5 July 2026
- Organiser
- IRONMAN
- Field size
- About 1,600 athletes
- First held
- 2021
- Distances
- 3.8 km (2.4 mi) swim, 180 km (112 mi) bike, 42.2 km (26.2 mi) run
- Cutoffs
- Finish 17:00
- Swim venue
- Lake Thun (start at the lido, exit at marina) (lake)
- Water temperature
- 16–18 °C (61–64 °F)
- Wetsuit
- Legal
- Swim start
- rolling
- Swim laps
- 1
- Bike climbing
- 1,906 m (6,250 ft)
- Bike laps
- 2
- Key climbs
- Toffen (biggest); Neuhaus (summit ~896 m) then 8 km technical descent; Kirchdorf ramp >12%; Uetendorf 8%; Hauptstrasse 4-5%
- Run climbing
- 79 m (260 ft)
- Run laps
- 3
- Run shade
- mixed; lakeside and park sections
- Air temperature
- 15–30 °C (59–86 °F)
- Humidity
- moderate
- Altitude
- 560 m (1,840 ft)
- Nearest airport
- Bern (BRN); most fly Zurich (GVA/ZRH) then train, 25 km (16 mi) away
- Where to stay
- Thun lakeside near Seepark, Thun old town / station, Spiez
- Booking
- Lodging near the venue is scarce and expensive; Spiez (10 min by train) or Interlaken (45 min) are cheaper fallbacks.
What racers and reviewers say
- Sport Over FiftyRaced 2022 · blog · Positive
Age-grouper's 2022 report: 18 °C (64 °F) wetsuit swim with a smooth rolling start but a crowded exit. Bike is about 2,200 m (7,220 ft) of gentle long grades on good pavement with a second-loop headwind. He faded on the run in ~26 °C (79 °F) heat and slept near the village. He still rated it the best-organized IRONMAN he had done.
“Best organized Ironman race I have done so far.”
- East Essex Tri ClubRaced 2022 · blog · Positive
Club member's 11:38 finish: clear 18 °C (64 °F) lake, a rolling start, a two-lap bike with rolling terrain and two long 4-5% climbs followed by fast descents. Run is three laps on tarmac, gravel, cobbles and an athletics-track loop. Heat built during the second bike lap, and he found crowds incredible all day.
- Athletica forumRaced 2024 · forum · Mixed
2024 finisher (16:06) describes a misty beach start in ~16 °C (61 °F) water with a slight swell and pre-race heat of 25-28 °C (77-82 °F). Bike was hilly with ~2,200 m (7,220 ft) of climbing and fast descents. He ranked it in the top half of eight long-course races and was not chasing time.
- Slowtwitch forumRaced 2023 · forum · Mixed
M45-49 athlete (18th in AG) in the 2023 heat wave: choppy, slow swim logged ~4.1 km (2.5 mi), significant bike climbing, and a punishing hot run where runners lived on Coke. Hydration planning dominated the day. Commenters felt it was still a good result with a World Championship slot.
- MediumRaced 2023 · blog · Mixed
Second 2023 age-grouper report (M40-44, 5:49 bike): swim measured ~350 m (1,150 ft) long, temperatures up to 36 °C (97 °F) on the bike, swollen feet, and a near-skid on a descent in a no-aero zone. Details taken from search-result excerpts only; the page itself could not be opened.
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- Slowtwitch forum: Best European IronmanRaced unknown · forum · Positive
US posters weighing European fulls: Thun called amazing but pricey, with a magnificent swim, beautiful bike on great pavement 'not as hard as you might think', closed roads and a clear cold lake. Hotel Seepark was recommended as walkable to the village. Hotels are hard to find and costly, with Spiez or Interlaken as fallbacks; one poster still preferred Nice or Lanzarote.
“Swim is magnificent with a postcard background.”
- Slowtwitch forum: EU full IM races sold outRaced unknown · forum · Mixed
Thread on why Thun is not selling out like other European fulls: posters blame Swiss hotel/food prices (~600 per night for a one-bedroom quoted), the move from August to July, and a hilly profile that makes PBs harder. Posters still call it one of the best and most beautiful IRONMAN races.
“one of the best IM races on the planet”
- PJAMM Cyclingarticle · Positive
Course analysis: two bike loops with ~52 turns per lap, good annually maintained roads, and named climbs (Uetendorf 8%, Kirchdorf ramp >12%, Toffen the biggest, Neuhaus summit ~896 m (2,940 ft) / 2,940 ft followed by a technical descent). Says the course is less hilly than it could be and is called by many their best IRONMAN experience; shuttle from 4:30 or 20-30 minute walk to the village.
“quite possibly the most beautiful race in the world”
- TriRatingRaced 2025 · aggregator · Positive
Data analysis of the 2025 pro race: conditions probably the fastest seen in Thun, with new course records (Arnold 7:49:20, Zepuntke swim 47:40, Bjerkeset bike 4:07:23). Course rating roughly even to the field average; 7 of 30 men did not finish.
- Plattform JRaced 2022 · article · Positive
Swiss press piece on the 2022 race (about 1,600 athletes from 53 countries): Ryf won in 8:59:05 and described the day as stunning but brutally hard. German-language, summarised from search excerpt.
“wunderschön, aber brutal hart”
- RaceCheck (Zurich era, not Thun)aggregator · Positive
Aggregated 4.45/5 average from seven reviews, all of the pre-Thun Zurich race (2008-2018). Praise for organization and scenic hills; complaints about cost of living. Included only as context for the brand's Swiss organization; none are of the Thun course.
- Congress Hotel Seepark Thun (via Nirvana Europe)hotel-review · Mixed
Lakeside hotel ~1 km (0.6 mi) from the finish line and expo village, with race-day early breakfast and in-room bike storage. One guest reported summer heat and an inadequate fan on humid days. Taken from a search excerpt.
Sources
Pages we used for facts and ratings. See how we rate.
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