A prolonged and severe heat wave is sweeping through the southeastern United States, pushing temperatures far above normal from central Florida to Virginia and prompting widespread health and safety warnings.

Forecasters have described the current heat levels as unusually harsh, even for an area familiar with sweltering summers.

The National Weather Service has issued heat advisories and extreme heat warnings across the region, covering parts of Georgia, the Carolinas, and up through eastern Virginia.

Heat index values, how hot it feels when humidity is included, are expected to rise to between 105°F and 110°F.

In parts of North Carolina, including Raleigh, and northeastern South Carolina such as Myrtle Beach, temperatures may reach or exceed 100°F.

Some locations could experience heat indexes as high as 115°F through Sunday evening.

More than 163 million people across the U.S. were under some level of heat alert as of Saturday afternoon, according to CBS News meteorologist Andrew Kozak.

On Friday, temperatures were already 10 to 15 degrees above the seasonal average for late July, with heat indexes topping 100°F in many areas.

Experts attribute the stifling heat to a high-pressure system known as a “heat dome,” which traps hot air over the region.

“The heat dome is creating persistent, oppressive conditions,” said William Gallus, a professor of atmospheric science at Iowa State University.

The National Weather Service has urged people to take precautions against heat-related illness.

“Drink plenty of fluids, stay in air-conditioned spaces, avoid direct sun, and check on the elderly and vulnerable,” it advised.

The agency also recommends wearing light, loose-fitting clothes and limiting outdoor activity to early morning or late evening hours.

Several cities, including Atlanta, Charlotte, Raleigh, and Greenville-Spartanburg, are expected to face extended heat with little relief even at night.

Authorities have warned that more than 30 million people could be exposed to dangerous temperatures into midweek.

The heat wave is also pushing into parts of the Midwest, with areas like eastern Nebraska, western Iowa, southern Minnesota, and the St. Louis region under extreme heat watches or warnings.

In St. Louis, temperatures are forecast to reach around 99°F on Monday and Tuesday, with heat indexes approaching 110°F.

In addition to the extreme heat, parts of Iowa saw heavy storms early Saturday, with rainfall between 2 and 5 inches, prompting flash flood warnings in affected areas.