A prolonged and dangerous heat wave is set to grip parts of Texas 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 Texas and Oklahoma before shifting west into parts of the Southwest later in the week. John Smith, 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 Dallas and Houston.

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 Texas, Oklahoma, Louisiana, Arkansas and southern Kansas as well as for portions of New Mexico, southern Colorado and central and southern Arizona. In Arizona, forecasters at the Phoenix 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 Amarillo, were expected to reach 109 degrees on Sunday and potentially up to four degrees higher on Monday. In southwestern Oklahoma and parts of western 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 New Mexico, southern Colorado 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. Johnson said had been centered over Texas since earlier in the week.

The system has already brought exceptionally hot conditions and several temperature records to parts of Texas, Oklahoma and New Mexico. The heat dome is expected to “just sit there” through at least the end of August and “probably into early September,” Mr. Johnson said, keeping the threat of extreme heat in place across the South.