Yr Wyddfa Sea to Summit
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Yr Wyddfa Sea to Summit mountain ultramarathon
The event is a one-day, mass-participation sea-to-summit ultramarathon on 26 September 2026. The route covers 29 miles (47 km) with approximately 5,600 ft of ascent, beginning inside Caernarfon Castle and finishing at Bron y Feds Uchaf, Rhyd Ddu (LL54 7YS). It is part of the Sea to Summit Trilogy series.
The course is fully waymarked with bright orange arrows and supported by event staff. There are multiple staffed pit stops that offer water, hot drinks, salty snacks, sweets and fruit, plus toilet and medical access. On-the-ground medical cover is provided by a professional event medic team, including paramedics and doctors operating from vehicles and a private ambulance. A GPS tracker is issued at Registration.
Cut-offs are set at a 3 mph pace; the route includes designated pit stops and contingency options. At Pit Stop 2 (about 12.6 miles) participants who miss the cut-off are directed onto a shorter summit route that makes the total distance about 20.5 miles with 5,175 ft of ascent. Pit Stop 3 (about 20.8 miles) is the last staffed stop before the mountain ascent. The course may be altered for safety or weather reasons; signage and arrows take precedence over GPX.
Participants must be over 18 on the day of Registration and carry mandatory kit such as a hydration system, headtorch, waterproof jacket, survival bag, basic first aid, full leg cover and a GPS tracker. The event offers a finisher medal and the option to earn a Trilogy gold medal by completing all three Sea to Summit events. Parking and shuttle options are available between the finish and the start. Visit the organization's website for the most recent information.
