More than 250 million people in the U.S.—nearly three quarters of the population—are experiencing moderate, major or extreme risk of heat effects on July 28, according to the National Oceanic and Atmospheric Administration’s National Weather Service.

A destructive derecho snapped trees and knocked out power to tens of thousands of people as it tore across portions of the northern Plains and Upper Midwest with hurricane-force wind gusts late Monday night and into early Tuesday morning.

Widespread heat indexes of 105 or higher will cover the eastern Plains, the Midwest, Mid-South and Southeast including Florida. Similar conditions are expected up the East Coast to the east of the Appalachians,

Senior Meteorologist Wesley Williams details the summer heat dome pattern and when our best rain chances will be.

The National Weather Service already has issued extreme heat warnings, watches and advisories across a swath of the Midwest and South.

For people under the sweltering influence of a heat dome, the weather pattern can be excruciatingly tedious to endure, Jackson told Scientific American. “Heat domes are generally slow to form and slow to dissipate,” he said.

July will make a potentially record-breaking exit this week as a heat dome will create triple-digit feels-like temperatures for millions from Florida to Virginia, prompting heat alerts across the East Coast.

Public health experts advise people to drink plenty of fluids, stay out of the sun, and check up on relatives and neighbors who may be vulnerable to the heat. Young children and pets should never be left unattended in vehicles under any circumstances.

The NWS has issued a bulletin warning that 100-degree temperatures will likely hit residents in the middle of the US today. The cause for that thermometer spike is a growing heat dome in the Mississippi Valley that should expand to the northeast by the end of the week, potentially affecting more than 100 million people, per Accuweather.

Heat dome continues over the South Carolina Midlands and afternoon storms could lead to localized flooding, depending on speed of storms