Half Distance Triathlon Weymouth, Dorset, England – Overview Swim: A 1.2-mile (1.9 km) one-loop triangular swim in Weymouth Bay. Average water temperature: 63°F (17°C). Bike: A 56-mile (90 km) anti-clockwise single loop through Dorset's rolling countryside, passing King's Stag, Godmanstone, and Dorchester. Run: A 13.1-mile (21.1 km) two-and-a-half loop course starting from Lodmoor Country Park, running along Weymouth's esplanade for a spectator-friendly finish. Average air temperature: 59°F ...