At least 100 million Americans are facing dangerous heat and humidity on Friday, affecting areas from Texas to Maine. Parts of the Eastern Seaboard are expected to feel like they are in the triple digits. Heat advisories are in effect from Texas to West Virginia, with temperatures forecasted to reach between 105 and 110 degrees.

In Boston, the heat index, which measures how hot it feels when humidity is factored in, could hit 103 degrees. New York City may feel like 104 degrees, while Washington, D.C., could experience a heat index of 109 degrees. The National Weather Service warns that these extreme temperatures could pose risks to anyone lacking adequate cooling or hydration. They also noted that there will be “little to no overnight relief.”

A cold front is expected to bring slight relief late Friday afternoon, accompanied by showers and thunderstorms that will lead to cooler temperatures in New England. However, the oppressive heat is projected to persist into the weekend and into next week, affecting regions from the Midwest to the Southeast. Heat indices could reach 113 degrees in parts of North Carolina and 110 degrees from St. Louis to Tampa. An extreme heat risk is anticipated from Sunday through Thursday for many areas in the Southeast.

While St. Louis grapples with the heat wave, parts of Kansas City, Missouri, are under a flash flood watch. Some areas were under a flash flood warning early Friday morning, with 1 to 3 inches of rain recorded by 4:30 a.m. The Kansas City Fire Department reported multiple vehicles stranded in high water, and at least 10 water rescues had been conducted by Friday morning.

Rain is expected to continue from southwest Kansas to central Illinois through Friday morning, but it should taper off in the afternoon. However, a redevelopment of the storm is likely later in the day, bringing additional heavy rain overnight and potential flooding to areas already affected.

In light of the extreme heat, the National Weather Service advises residents in impacted areas to limit outdoor activities, stay hydrated, and ensure access to air conditioning or other cooling facilities.