(NewsNation) — A large dome of intense heat and high humidity will remain in place today over much of the Mississippi, Tennessee and Ohio valleys. Many areas from the Great Lakes to the Gulf Coast and in the Carolinas will approach or exceed 100 degrees in this zone.

On the rim of the heat from parts of the northern Plains to the eastern Great Lakes, central Appalachians and lower mid-Atlantic regions, thunderstorms will be on the move. The storms in parts of the mid-Atlantic may be intense enough to be classified as derechos. Thunderstorms could also reach parts of the interior Southeast.

Severe storms yesterday knocked out power across southern Wisconsin and Michigan through Indiana, Ohio and West Virginia Monday evening, leaving more than a half-million customers without power late Tuesday morning.

And with record heat on the way today, NewsNation meteorologist Gerard Jebaily is concerned a life-threatening situation may be brewing. He said excessive heat warnings are in place, and the elderly are especially at risk.

“Remember that heat is weather’s No. 1 killer: More than tornadoes, more than severe weather, more than flooding. And with the combination of heat and no power, it makes it especially dangerous across these regions.

Temperatures in the affected area will be in the upper 90s, with heat indices as high as 110.

Cool air is forecast to hold its ground over New England and expand over much of the West.

Pacific moisture will lead to areas of showers and thunderstorms over the interior Northwest, with snow over the parts of the high country in Montana, Idaho and northwestern Wyoming.