IRONMAN Western Australia
Course breakdown, historical weather, and field analysis.
Busselton Jetty swim, two laps through Tuart Forest, foreshore marathon
Busselton, Australia · December 6, 2026
IRONMAN Western Australia pairs a Busselton Jetty swim in Geographe Bay with a flat 180 km two-lap bike along the coast and into Tuart Forest National Park, and a multi-lap marathon along the foreshore. One of the flattest 140.6 courses on the IRONMAN circuit — wind, not gradient, is what shapes the day.
- Swim
- 3.8 km
- Sheltered ocean
- Bike
- 180.4 km
- ↑79m · Flat
- Run
- 42.4 km
- ↑65m · Flat
- Air Temp
- 11–26°C
- Water Temp
- 20°C
- Wind
- 21 km/h
- S
Swim Course
Busselton Jetty swim in the sheltered waters of Geographe Bay
The 3.8 km swim runs alongside the Busselton Jetty in the sheltered waters of Geographe Bay. Water sits around 19–20°C in December, with the bay's sheltered nature keeping conditions calm relative to the open Indian Ocean on the jetty's far side.
- Alongside the Busselton Jetty
- 3.8 km in sheltered Geographe Bay
- Water ~19–20°C in December
- Sheltered bay conditions
Bike Course
Two-lap flat bike along the coast and through Tuart Forest
The 180 km bike is a two-lap course: each lap heads out along the Geographe Bay coast and into Tuart Forest National Park before returning. Terrain is flat — 79 m of gain over the whole 180 km — so the variable that matters here is wind, not gradient. The prevailing summer sea breeze sits at ~21 km/h from the south-southeast on average, and how it interacts with the two-lap shape decides whether the day runs fast or slow.
- Two-lap course — 79 m of gain over 180 km
- Along Geographe Bay coast and into Tuart Forest National Park
- Prevailing ~21 km/h south-southeast sea breeze
- One of the flattest 140.6 courses on the IRONMAN circuit
Run Course
Multi-lap marathon along the Busselton foreshore
The marathon is a multi-lap course along the Busselton foreshore, hugging Geographe Bay throughout. Terrain is flat — 65 m of gain over 42 km — but flat doesn't mean free: a marathon off a fast bike still punishes anyone who arrives at T2 with too much spent, and on a course this exposed the sea breeze hits the field on every lap.
- Multi-lap along the Busselton foreshore
- Flat — 65 m over 42 km
- Coastal: Geographe Bay views throughout
- Flat course, but bike overspend still costs the run
Race Day Conditions
Early Australian summer — mild conditions, persistent sea breeze
Early December in Busselton is typically mild — daytime around 21°C on average, with the day's range widening from cool morning starts in the low-teens to mid-20s afternoons. The defining weather feature is the persistent south-southeast sea breeze, averaging ~21 km/h. On a course where 79 m of bike elevation means wind decides the bike split more than climbing does, that breeze is the variable to plan around.
Race Field Insights
How the Field Performs
Aggregated from 4,455 finishers (2022–2025)
- Total Starters
- 4,744
- Finishers
- 4,455
- DNF Rate
- 5.9%
- Years of Data
- 2022–2025
- Median Finish
- 12h 04m
Finish Time Distribution
How the Median Finisher Spends Race Day
What Each Pace Looks Like
Fast | Solid | Median | Back of Pack | Slow (P90) | |
|---|---|---|---|---|---|
| Swim | 1h 01m | 1h 08m | 1h 18m | 1h 28m | 1h 41m |
| Bike | 4h 59m | 5h 23m | 5h 53m | 6h 27m | 7h 02m |
| Run | 3h 32m | 3h 56m | 4h 33m | 5h 20m | 6h 06m |
| Finish | 9h 53m | 10h 51m | 12h 04m | 13h 35m | 14h 59m |
Related reading
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Read postWhy Most Triathletes Blow Up on the Run (And It Has Nothing to Do with Running)
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Read postPlan IRONMAN Western Australia with Keiro
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Independent analysis. KeiroLabs is not the event organizer and is not affiliated with the race organizer.