US heat wave eyes Northeast amid severe storms: Latest forecast

More than a third of the United States is on alert for hot temperatures amid a deadly heat wave that has plagued the country for weeks.

The National Weather Service has issued heat alerts that are in effect Wednesday morning for 120 million Americans across 27 states, from California to Massachusetts.

The weather forecast for Wednesday shows temperatures heating up particularly in the middle of the country, an area that's had a relatively seasonal summer so far. By the afternoon, temperatures are expected to be near, at or above 100 degrees in cities like Minneapolis, Minnesota; Sioux Falls, South Dakota; and Manhattan, Kansas.

Heat index values -- a measure of how hot it really feels when relative humidity is combined with the air temperature -- are forecast to be in the 100s throughout the week from Kansas City, Missouri, to Washington, D.C.

The heat is expected to stretch into the Northeast later this week, with temperatures peaking on Friday. New York City could see its first heat wave of the season with high temperatures in the 90s on Thursday, Friday and Saturday. A heat alert will go into effect there on Thursday. Heat index values could range from 100 to 112 degrees in the greater Interstate 95 travel corridor.

The latest forecast shows the heat will start to slowly push back south over the weekend and through much of next week. The Gulf Coast will feel the scorching temperatures, while the North and Northeast cool back down.Even the Southwest may see an end to the record heat streaks.

Arizona's capital is on a record stretch of 26 consecutive days with temperatures at or above 110 degrees. Overnight temperatures in Phoenix have also not dropped below 90 degrees for at least 16 days. The city hit 119 degrees on Tuesday, breaking a daily record of 116 degrees set in 2018.

Arizona's Maricopa County, which includes Phoenix, has had a total of 25 confirmed heat-associated deaths so far this year. Another 249 deaths are currently under investigation as potentially heat-related, according to data released Wednesday by the Maricopa County Department of Public Health.

Tucson, Arizona, has been at or above 100 degrees for a record 40 days in. a row. The city's previous record of 39 straight days was set in 2013. The city also hit 112 degrees on Tuesday, breaking a daily record of 110 degrees set in 2018.

El Paso, Texas, has been on a record-smashing stretch of 40 consecutive days with temperatures at or above 100 degrees. This is expected to continue this week and may finally come to an end over the weekend. The city's previous record of 23 consecutive days was set in 1994.

Miami, Florida, has had a heat index high of 100 degrees for a record 45 days in a row, well past the previous record of 32 days set in 2020. The wider Miami-Dade County has been under heat Advisories and excessive heat warnings for a record-smashing 22 days. The previous record was just three days. South Florida, as a whole, is on pace to have its hottest July on record.

Meanwhile, a severe storm system is expected to hit the southern Great Lakes region on Wednesday before taking aim at the Northeast on Thursday.

The weather forecast for Wednesday shows a severe threat of damaging winds, large hail and a few tornadoes from Chicago, Illinois, to Cleveland, Ohio, including the cities of Detroit, Michigan, and Fort Wayne, Indiana. The storm system is expected to enter the Detroit area after 4 p.m. ET before reaching Cleveland after 7 p.m. ET.

That severe threat is forecast to shift over to the Northeast on Thursday, from Washington, D.C., to Portland, Maine. The storm system is expected to enter the area sometime in the afternoon and evening.

ABC News' Jennifer Watts contributed to this report.