IRONMAN wetsuit rules and water temperature

• Up to 24.5 °C (76.1 °F): wetsuits are allowed. Below 16 °C (60.8 °F) they are compulsory.
• From 24.6 °C to 28.8 °C (76.2 to 83.8 °F): no wetsuit in the competitive race. IRONMAN may, at its discretion and for some events such as those sanctioned by USA Triathlon, open a separate non-competitive wetsuit wave. Athletes in that wave are not eligible for age-group awards or World Championship slots.
• Above 28.8 °C: wetsuits are banned.

These thresholds come from section 4.02 of the 2026 IRONMAN Competition Rules. The temperature is measured on race morning, and the organiser announces the decision before the start. Professional athletes may wear a wetsuit up to 21.9 °C. Maximum thickness is 5 mm. Neoprene booties are allowed only at 18.3 °C or colder (section 4.01), and a neoprene cap only when wetsuits are allowed.

The IRONMAN Competition Rules govern every IRONMAN and IRONMAN 70.3 race, so the thresholds are the same over the 1.9 km swim of a 70.3 as over the 3.8 km of a full distance. Of the 114 IRONMAN 70.3 races with a water average, 89 sit at 24 °C or less and 25 at 25 °C or more. The 70.3 table above lists them from the coldest.

Across the 158 IRONMAN races with a figure, 126 average 24 °C or less, where a wetsuit is almost always allowed, and 8 average 29 °C or more, where it is almost always banned. The rest sit in between, where the morning reading decides.

An average is not the reading. A cold night or an upwelling can drop a sea swim by several degrees; a heatwave can lift a lake. Train for both answers when your race sits near 24.5 °C.

IRONMAN Cozumel shows the gap: an average of 26 °C, but 24 °C measured on race morning in 2023. The IRONMAN in Mexico page gives the race-day readings that ironman.com publishes for Mexican races, and the IRONMAN in the USA page does the same for races such as Lake Placid, Oceanside and Florida. The IRONMAN in Australia page gives them for Busselton, Cairns, Geelong and Western Sydney.