What is the water temperature at Jeju Triathlon 70.3 and can I wear a wetsuit?

The swim takes place in lake water with an average temperature of 16°C during race month. Wetsuits are conditional — typically depends on race-day water temperature.

How hilly is the Jeju Triathlon 70.3 bike course?

The 90km bike course has 1177m of elevation gain and is classified as hilly. The course is loop on road surface. Drafting is not allowed.

What is the weather like on race day at Jeju Triathlon 70.3?

Expect temperatures between undefined°C and undefined°C (average 21°C) with 78% humidity. There is a 38% chance of rain and average wind speeds of 20 km/h. Typical conditions in Jeju

How big is the Jeju Triathlon 70.3 and when was it first held?

The Jeju Triathlon 70.3 was established in 2017 (9 years ago) and has approximately 1,722 finishers per edition.

What is the average finish time for Jeju Triathlon 70.3?

The average finish time is approximately 5 hours and 30 minutes. This can vary based on weather conditions, course difficulty, and athlete experience level.

What are the swim conditions like at Jeju Triathlon 70.3?

The 1900m swim is in lake water with calm conditions. The format is open-water. Lake swim in Jeju

Jeju Triathlon 70.3 — Guide, Training Plan & Tips

Average Finish Time 05:30:00

Total Finishers 1.722

Temperature 21°C

Water Temperature 16°C

Bike Elevation ↑1177m

Established 2017

"Lake swim and mountain bike in Jeju, South Korea."

🏊 Swim

Distance 1900m

Water lake (open-water)

Water Temp 16°C

Wetsuit conditional

Lake swim in Jeju

🚴 Bike

Distance 90km

Elevation ↑1177m

Profile hilly

Drafting Non-drafting

Hilly bike course around Jeju

🏃 Run

Distance 21.1km

Elevation ↑176m

Surface road

Topology out-and-back

Run through Jeju

Transition Details

T1 — Swim → Bike

T2 — Bike → Run

T1/T2 are in the same location · Surface: pavement

Weather

Air Temp 21°C

Humidity 78%

Rain Chance 38%

Wind 20 km/h

Typical conditions in Jeju

Registration

Registration Opens Invalid Date

Entry Cost €437

Time Limit 8.5h

https://www.example.com/jeju-triathlon-70-3

The Story

Seventy point three miles through Jeju. That's 1.9km in the water, 90km on the bike, and a half-marathon to finish — the world's most popular triathlon distance, in a city that earns the right to host it. The 1.9km swim sends you into cool still lake waters at 16°C — cool enough to want a wetsuit, warm enough to swim without panic. It's long enough that a poor start costs real time, short enough that strong swimmers can build a genuine lead. The 90km bike is the defining leg: 1177m of elevation gain across a mountainous course that separates those who trained for this specific distance from those who just showed up fit. Ninety kilometres of climbing changes the race equation entirely. The 21.1km run rolls through Jeju, adding 176m of climbing to legs already tested by the bike. The undulations are psychological as much as physical — each rise feels larger than it is when you've been racing for four hours. That's the deal, and it's a good one.

"The swim wakes you up, the bike breaks you down, and the half-marathon shows you who you really are. That's 70.3 in Jeju."

Age-group athlete — Post-race, Jeju Triathlon 70.3

What It Feels Like

A 70.3 that reflects Jeju: volcanic island beauty with Korean efficiency. It suits experienced 70.3 athletes who want a course that fights back. This isn't a PB course — it's a character-building one. Race it once and you'll understand why 70.3 is the distance athletes come back to, year after year.

🏊 The Swim

A 1.9km freshwater lake swim at 16°C. No salt, no currents, no tide — just you and 1,900 metres of open water. Lake swims reward smooth bilateral breathing and consistent sighting. Cool enough to want a wetsuit, warm enough to swim without panic. The calm surface makes drafting easier to find and hold.

🚴 The Bike

90km with 1177m of climbing — a mountainous bike course that makes the 90km the race's decisive leg. Power-to-weight matters more than pure wattage. The climbs test your legs; the descents test your nerve. Come with a compact crankset, climbing legs, and the discipline to save something for 21.1km of running.

🏃 The Run

A 21.1km rolling run through Jeju with 176m of gain. The undulations feel disproportionate on legs that have just covered 90km of bike. Keep cadence quick on the ups, use the downs to stretch your stride, and run the tangents. In warm 21°C conditions, each hill amplifies the heat cost. Walk an aid station if you need to — it costs 15 seconds and gains you proper hydration.

💡 Insider Tips

→ At 16°C, the water is cool enough to tighten your breathing on entry. Practice cold-water starts in training — jump in and swim 200m hard, then settle. The 1.9km swim is long enough that early panic costs minutes, not seconds.
→ Average winds of 20 km/h make the 90km bike the decisive leg. Stay low and committed to your aero position. Avoid deep-section front wheels in crosswind sections. Hold power, not speed — chasing pace into a headwind is the most common 70.3 pacing mistake.
→ The bike packs 1177m of climbing over 90km — that's a real day in the saddle. Keep cadence above 80rpm on the climbs and resist the urge to hammer. Every watt you spend above threshold on the bike comes out of your half-marathon. A compact crankset with a 28+ cassette is non-negotiable.