Heat wave to scorch the U.S. this week — and some cities will experience ‘feels like’ heat index of 115°F

A dangerous heat wave continues to scorch a large part of the United States, with more than 130 million people under extreme heat watches and warnings from South Dakota to Florida as temperatures in some cities are expected to exceed 100 degrees, and heat indexes — or “feels like” temperatures — could soar past 115°F.

The so-called heat dome that baked much of the Midwest last week has now settled over the Southeast, where intense and potentially life-threatening heat and humidity are expected to continue through at least Wednesday.

How hot will it feel, exactly?

From Charlotte, N.C., to Orlando, heat indexes, or what the temperatures feel like when humidity is factored in, are forecast to be between 108° and 116°F for multiple days.

And temperatures at night won’t provide much relief. Overnight lows are expected to fall only into the 70s across the region.

According to the National Weather Service’s HeatRisk monitor, more than 18 million people across five states — North Carolina, South Carolina, Georgia, Alabama and Florida — were under the highest risk level (four out of four) for extreme heat on Monday. More than 130 million people — from the Midwest to the Northeast — were considered in the “major” (three out of four) risk level.

Such levels are “dangerous for anyone without adequate cooling or hydration,” the weather service warned, noting that the risk of heat-related illnesses increases significantly with prolonged exposure to extreme heat and humidity.

What you can do to protect yourself

“Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors,” NWS advised. “Take extra precautions when outside. Wear lightweight and loose-fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke.”

When will the heat wave break?

There is, however, some relief on the way. According to the long-range forecast from the weather service, a strong cold front is expected to usher in cooler temperatures across much of the eastern U.S. by next weekend, with highs 10-20 degrees below what they were earlier in the week, and much lower humidity.

Wildfire risk out West

Meanwhile in the Western U.S., there is an increasing risk of wildfires, as high winds and extremely low humidity are forecast for portions of Colorado and Utah, where red flag warnings have been issued.

According to the NWS in Salt Lake City, the relative humidity is expected to be as low as 8% on Monday, with wind gusts above 30 mph.

In addition, a series of storms with lightning but little to no rain could increase wildfire activity.

“Lightning strikes from thunderstorms could spark fires,” Accuweather warned. “In storms that bring little to no rain, there is no moisture to put out the emerging fires. Gusty winds that accompany the thunderstorm in the immediate vicinity then fan the flames and cause the fire to quickly spread.”