The story

Weather warnings are in place for millions of Americans this week as storms and heavy rain pummel the mid-Atlantic states and the Carolinas while a heat wave intensifies and expands. More than 100 million people are expected to fall under some sort of heat watch or warning this week, while millions more are forecast to be cautioned about their risks for heavy rain or potential flash flooding, according to the National Oceanic and Atmospheric Administration. Tropical Storm Bertha is helping to push tropical moisture into the eastern United States, where it is colliding with a strong cold front to generate flash flood warnings and repeated bouts of storms through Friday for a region stretching from Kentucky and West Virginia eastward to New Jersey and as far south as the Carolinas.

Rainfall is forecast to range from 2 to 5 inches across the larger region, but there is potential for up to 8 inches of rain in the Hampton Roads area of Virginia and over eastern North Carolina. The front is expected to soak and potentially cause flash flooding in the Hampton Roads area, including Norfolk and Virginia Beach, on July 22 before shifting southward into the Carolinas on July 23 through 24. Nashville is under a heat advisory until 8 p.m. July 21, with a heat index upward of 110 degrees, followed by a severe weather threat capable of producing heavy wind gusts, a lot of rain and a possible tornado.

An extreme heat warning is in effect for Southeast Texas, including the Houston metro area, from 11 a.m. to 8 p.m. Wednesday, with heat index values reaching 115 or 116 degrees. Several consecutive days of hazardous heat are expected because of the combination of afternoon high temperatures and warm overnight lows, with overnight lows possibly being record-breaking. Twelve states are under extreme heat warnings on July 21, including Arkansas, California, Illinois, Indiana, Kansas, Kentucky, Louisiana, Mississippi, Missouri, Oklahoma, Tennessee and Texas. The weather service is urging people to limit their outdoor activities during the hottest afternoon hours and to stay hydrated.