A long and dangerous heat wave will blast a large swath of the central and eastern United States this week, the National Weather Service said, with temperatures rising ahead of the July Fourth holiday and feeling even hotter because of the high humidity that’s arriving with it.

Already, parts of the U.S., especially Phoenix and central Texas, and much of the Southwest were experiencing temperatures around 100 F (38 C) on Sunday, while the weather service warned of severe wildfire conditions developing across much of the West as new fires popped up across the region.

On Sunday, well over 130 million Americans across southern and Great Plains states were under moderate to severe heat risk conditions, according to weather service maps, with that area forecast to expand and temperatures to intensify as the week drags on.

Forecasters say several days of high temperatures — some above 100 degrees F — will settle in across the lower Great Lakes, the mid-Atlantic and the Mississippi and Ohio River valleys. Some record highs could be set in areas from the lower Great Lakes to the mid-Atlantic and New England later in the week, said weather service meteorologist Bryan Putnam.

A number of big cities could see their highest temperatures of the year so far as they host World Cup matches and celebrations for America’s 250th anniversary.