"A dangerous, widespread heat wave will bake the central and eastern U.S., bringing the hottest temperatures of the year and uncomfortably muggy air to the Midwest and Northeast that in some areas could last into much of next week," Weather.com meteorologist Jonathan Erdman said in an online forecastJune 20. AccuWeather estimates that 170 million people will experience temperatures at or above 90 degrees during the building heat wave into next week. "The magnitude and longevity of this heat wave will be a shock to the system," AccuWeather senior meteorologist Chad Merrill said.