But It’s Only June: An Early Blast of Heat Grips Much of the U.S.

Larry White was thrown a little off-kilter by the soupy, 93-degree temperature in Chicago on Monday morning. It’s only mid-June, he said with annoyance, and until this week he barely needed the air-conditioning in his high-rise apartment on the city’s North Side. When he stopped at McDonald’s, he ordered a large hot coffee out of habit.

“What am I doing with this?” Mr. White said. He studied the skin on his forearm, already glistening with sweat. “Barely starting the day and I’m getting burned.”

A heat wave that is expected to punish much of the country before week’s end enveloped the Midwest, leaving the region scorched and sweltering.

In Chicago, beaches were packed by midmorning, and in a stroke of good luck, Monday was the first day that hundreds of city pools, water playgrounds and splash pads opened for the summer.

While a Midwestern heat wave in mid-June is not unprecedented, this one is striking in its duration, said Jake Petr, the lead forecaster with National Weather Service Chicago, and may augur another brutal summer. Most of the country is expected to see temperatures higher than usual for the next three to four weeks, forecasters said.

The heat is moving quickly to the Northeast. Meteorologists said the temperatures would peak on Thursday or Friday, with heat indexes exceeding 100 degrees in New Jersey, Pennsylvania, New York and Connecticut.