While parts of the South may get a brief break in the extreme heat this week, the Pacific Northwest is sweltering and the National Weather Service warns record-breaking temperatures will expand into the Central U.S. by Friday.

Continued heat and drought conditions in Louisiana prompted Governor John Bel Edwards to declare a statewide emergency on Monday, as much of the South endures an ongoing heat wave.

The weather service has issued "a record number of excessive heat warnings for Louisiana" this summer, Edwards said. And heat-related emergency room visits have exceeded the annual average, according to the state's health department.

While an emergency declaration is an administrative step that allows governments to direct resources to respond to emergencies, the Louisiana declaration also underscores the continued danger of heat baking parts of the nation.

Heat advisories and excessive heat warnings were in place in more than a dozen states Tuesday, stretching throughout the south and Pacific Northwest.

With more than a dozen Louisiana parishes under excessive heat advisories, Edwards urged residents to take precautions when outside and check on neighbors who might need assistance.

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What's the forecast for the Pacific Northwest heat wave?

• Heat watches and warnings are in effect across Oregon, Washington, Idaho and northern central California.
• The heat this week may lead to one of the hottest four-day stretches on record, the weather service said.
• High temperatures are expected to be in the low 100s for most interior locations, with potentially record-breaking heat day and night.
• The areas at greatest risk include the interior valleys and lower elevations of western Oregon, including Portland, Salem, Eugene, the Willamette Valley and Medford.

What's the forecast for the heat wave in the South?

• While some parts of the South are seeing temperatures ease a little this week, excessive heat is forecast to continue in portions of Texas and southern Florida, the weather service said Tuesday.
• In the hottest areas, heat indices in the triple digits could continue.
• Excessive heat is forecast to return to a larger area of the Southeast by early next week.

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