You’ll hear the term “heat dome” a lot this week as a pattern of very hot temperatures and dangerous heat indices set up across a good portion of the US. A heat dome is strong area of high pressure and warm air that essentially sits over an area for a prolonged period

More than 95 million people are under heat alerts as a dangerous heat dome expands. Ash-har Quraishi reports from Chicago, where temperatures are already climbing.

More than 97 million people are under life-threatening heat alerts from the South to the East Coast as a large ridge of high pressure builds over the central U.S. this week, commo

The National Weather Service has issued a Heat Advisory for Kent and Sussex counties, and an Extreme Heat Watch for New Castle County, as the heat dome is expected to impact Delaware on Friday. The Heat Advisories and Extreme Heat Watch will be in effect from 10 a.m. to 8 p.m. on July 25.

Heat domes are caused by high-pressure systems that trap air near the surface of the Earth, sealing in hot, humid air and stopping cooler air from cycling through.

The big weather story this week is a large area of high pressure building over the central U.S., often called a “heat dome,” the FOX Forecast Center warns.

A heat dome dries out the ground and air above it, which deters thunderstorms, but means drought can begin or worsen. A heat dome is also known as a ridge of pressure, blocking high and death ridge.

While Texas bakes under sweltering conditions, it's far from alone. Millions are under threat of extreme heat this week.