A prolonged and dangerous heat wave is set to grip parts of the Southern United States this week, as forecasters warned that temperatures are expected to soar into triple digits, with daily records at risk of being broken.

The most intense heat is initially expected across the Southern Plains and Lower Mississippi Valley before shifting west into parts of the Southwest later in the week.

Bob Oravec, a meteorologist at the Weather Prediction Center, said temperatures were expected to reach or exceed 100 degrees across large parts of the region, with several daily record highs possible, particularly in Texas and Oklahoma.

The heat will not ease much after sunset, with much of the South expected to remain above 80 degrees for several nights in a row.

The Weather Prediction Center issued extreme heat warnings and heat advisories across large areas of Louisiana, Mississippi, Oklahoma, Texas and southern Arkansas as well as for portions of Southern California, southern Nevada and central and southern Arizona.

In Texas, forecasters at the Fort Worth office of the National Weather Service said the hottest days of the summer were likely in the coming days.

Temperatures in north-central Texas, including Dallas, were expected to reach 109 degrees on Sunday and potentially up to four degrees higher on Monday.

In southwestern Oklahoma and parts of western North Texas, highs up to 115 degrees are possible through Monday.

Farther west, the heat is expected to become even more intense later in the week.

Extreme heat warnings were in place across parts of the Southwest through Saturday, with temperatures above 110 degrees expected each day in parts of southeastern California, southern Nevada and central and southwestern Arizona.

Highs of 115 to 118 degrees are possible, including for the Phoenix metropolitan area, starting in the middle of the week.

The extreme heat is being driven by a large high pressure system — often referred to as a heat dome — that Mr. Oravec said had been centered over the Southern Plains since earlier in the week.

The system has already brought exceptionally hot conditions and several temperature records to parts of Arkansas, Oklahoma and Texas.

The heat dome is expected to “just sit there” through at least the end of August and “probably into early September,” Mr. Oravec said, keeping the threat of extreme heat in place across the Southern United States.