Southwest heat wave simmering since spring will expand to cover much of US

A heat wave simmering in parts of the Southwest since spring was expected to expand into the central and eastern portions of the nation for the last week of July, forecasters said Sunday.

"For much of July hot dangerous conditions have been the normal in parts of the West, Texas and Florida," the National Weather Service said in a forecast discussion. "These summer conditions will build and expand across the Eastern two-thirds of the country this week, starting in the north-central states and Plains."

Federal forecasters have issued excessive heat warnings and heat advisories for a wide swath of the United States, including parts of California, Utah, Nevada, Colorado, Oregon, Idaho, Wyoming, Nebraska, the Dakotas, the desert Southwest, Texas, and the southern tip of Florida. 

Three high pressure systems of the type associated with hot weather were expected to move over the interior West, the Midwest and Northeast, and Florida, according to the weather service.

The heat wave's geographic expansion through at least Wednesday could be dampened by expected thunderstorms in the Mid-Atlantic, the South, and along the Gulf Coast, the weather service said.

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