Volatile summer weather threatens to turn World Cup into test of heat

June 10 : The World Cup will kick off on Thursday under familiar North American summer threats: extreme heat, suffocating humidity and thunderstorms capable of delaying matches with little warning.

Seasonal forecasts indicate above-normal temperatures across large parts of the United States, while moisture flowing north from the Gulf of Mexico could fuel thunderstorms and severe weather during the opening weeks of the tournament.

While conditions for individual matches cannot be predicted this far ahead, sports scientists say there are clear weather-related risks facing a summer World Cup spanning Canada, Mexico and the United States.

The key measure is not air temperature alone but wet-bulb globe temperature, which incorporates heat, humidity, sunlight and wind to estimate heat stress on the body.

World Weather Attribution has warned that roughly a quarter of matches could be played in conditions that exceed recommended safety limits.

INTERNAL HEAT CHALLENGE

Chris Minson, a physiology professor and co-director of the Exercise and Environmental Physiology Labs at the University of Oregon, said elite players generate enormous internal heat even before the weather is considered.

"Seventy-five percent of all the energy that we utilise during exercise gets converted to heat," Minson told Reuters. "Only about 25 per cent goes to actually doing the exercise."

In hot, sunny or humid conditions, the body's normal cooling system begins to struggle. Humidity is a particular concern, since sweat cools the body only when it evaporates.

"One of the hardest things for us is when the humidity is very high," Minson said.

High-humidity World Cup venues include Houston, Miami, Dallas and Monterrey.

CLIMATE CHANGE IMPACT ON PERFORMANCE

Climate change