Hot weather will be a major concern at the World Cup, but lightning may also prove a particular problem. Under US safety regulations, a strike within 10 miles (16km) of a stadium triggers a 30-minute suspension of the game, during which players must leave the pitch.
The size of the safety zone was dictated by research on the distance that lightning can strike from a storm even with no clouds overhead. This is more than a theoretical risk. During a game in the Democratic Republic of the Congo in 1998, an entire team was killed by a single bolt of lightning. There have been many other deadly incidents.
