Heat dome to spread across the United States this week

(CNN, KYMA/KECY) - The U.S. has entered the peak of summer and a new heat dome, sealing in all that hot, humid air, is about to settle in over the nation.

Some cities could notch their highest temperatures of the year as heat builds from the South to the Midwest this week.

Humidity is expected to drive the heat index, or how hot it will actually feel, well into the triple digits.

That "apparent temperature" is expected to soar to dangerous levels for tens of millions of people.

Sizzling conditions will begin to build from the Gulf Coast to the Plains Tuesday.

They will ramp up in intensity and expand to the Midwest on Wednesday.

Brutal heat will stretch from the south through the Midwest on Thursday and also begin to push into the East.

The most intense heat for the East Coast is expected to arrive by Friday.

For many, the heat dome will ease by Saturday.

It will be replaced by more typical late July temperatures.