A dangerous heat wave will hit the eastern United States this week as the FIFA World Cup enters a key knockout stage before the Fourth of July weekend. Forecasters warn that extreme heat and high humidity could affect players, fans and power supplies across the region.

Temperatures will reach 90F (32C) in Newark, New Jersey, on Tuesday. The heat will arrive just hours before a knockout match at the open-air MetLife Stadium. By Thursday, a heat dome will push triple-digit temperatures from Washington to Boston.

The National Weather Service has issued excessive heat alerts across more than two dozen states. Forecasters also expect hundreds of daily temperature records to fall. High humidity will make the weather feel even hotter. Little cooling is expected overnight.

“Our bodies can’t regulate when the air is so saturated, with how muggy it is,” said AccuWeather senior meteorologist Tyler Roys.

“The risk of heat-related illness will spike across the board, not just for the elderly.”

Players and fans face difficult conditions

The hot weather will also affect World Cup matches in Canada. Toronto will host Portugal and Croatia on Thursday evening. Temperatures there could reach 90F. Commodity Weather Group said heat and humidity could push temperatures up to 8F above normal across parts of eastern North America.

FIFA has already introduced water breaks during matches because of heat concerns. FIFPRO has also advised organisers to delay matches if heat stress rises above safe limits.

Afternoon thunderstorms could create more challenges during games.

“Weather does play a role in both our oddsmaking and customer-betting behaviour,” said Johnny Avello, director of sports operations at DraftKings Inc.

Power grid under pressure

The heat will also increase electricity demand. PJM Interconnection LLC expects a record power demand of 166 gigawatts on Thursday. The grid operator serves about 67 million people across 13 states. It has asked the Department of Energy to allow all power plants to operate at full capacity.

Officials say the power grid already faces heavy pressure this summer as demand from data centres continues to grow