Record heat will bake much of the East the next few days, then will also flare up this weekend in parts of the Northwest as summer's warmth expands to other parts of the U.S.

Heat alerts in effect

Heat advisories have been posted in parts of the East and West as the map below shows. This includes New York City, Philadelphia, Baltimore, Seattle and parts of California's Central Valley.

A heat advisory is the lowest level heat alert issued by the National Weather Service. This means the combination of heat and humidity could be hazardous to those particularly susceptible to the heat.

An extreme heat warnings has been issued for the Portland, Oregon, metro from about midday Sunday through Tuesday night.

This highest level heat alert means dangerous heat is forecast to happen, and that all should minimize their time outside, especially during the hottest part of the day.

East record heat details

The searing heat has arrived in the East, and it could threaten dozens of daily record highs from Georgia to New England.

Highs in the 90s could stretch as far north as Vermont, and some 100s are possible in parts of Virginia and the Carolinas.

New York City, Philadelphia and Washington, D.C. are just some of the East Coast cities that could set daily records. Raleigh could have one of its earliest-in-season 100-degree highs on record in this heat wave. Its record earliest 100 was on June 3, 1895.

While the peak of the record heat will be Friday, hot and humid conditions will linger near the East Coast this weekend. A few records could still be threatened this weekend from parts of southern Virginia to the Carolinas.

Relief from the heat should begin arriving in the interior Northeast Sunday, then progress to the East Coast, then Southeast Monday into Tuesday.

(MAPS: 10-Day US forecast highs and lows)

Northwest joins the heat parade

This weekend will turn hotter in the Northwest, from Oregon and Washington to Northern California.

Highs will soar well into the 80s in Seattle and Spokane, and will surge well into the 90s in parts of western Oregon, including Portland, Salem and Eugene. Daily record highs are possible in these areas through at least Monday.

Triple-digit highs are also expected in California's Central Valley, including Sacramento.

Heat relief arrives in the Northwest Tuesday and Wednesday.

What is causing this heat?

The eastern U.S. heat is being drawn northward ahead of a strong cold front that will eventually sweep through.

In the West, an expansive area of high pressure above the ground with sinking, dry air known as a heat dome will form near the Northwest Coast, giving rise to the heat wave.

And what is making the heat feel worse in the eastern two-thirds of the country? The humidity.

Dew points in the 60s and 70s are only going to make these 90s feel more oppressive. Feels like temperatures could flirt with triple digits for several days.