These US regions will be experiencing extreme heat Sunday

Extreme heat is continuing to impact a large portion of U.S. residents.

The National Weather Service issued heat alerts for about one-third of Americans on Sunday, as temperatures continue to remain at dangerous triple digits for millions. More than 115 million Americans are under heat alerts across 16 states.

The heat index in the South is expected to reach 105 to 115 throughout nearly the entire region, while the Northwest will experience a surging heat wave as well due to a high-pressure system expanding into the region.

Daily records are possible in more than 30 places on Sunday, including Portland and Medford, Oregon; Dallas, Austin, Texas, and Houston; Shreveport, Louisiana, and Baton Rouge, Louisiana; Jackson, Mississippi; Mobile, Alabama; Albany, Georgia, and Savannah, Georgia; and in Florida, Jacksonville, Tampa and Orlando, forecasts show.

Sunday's heat will be a continuation of the last several weeks of record-breaking temperatures.

Record daily high temperatures were recorded Saturday in New Orleans, at 100 degrees; Orlando, at 100 degrees; Naples, Florida, at 98 degrees; and San Antonio at 105 degrees, according to the NWS.

Temperatures have been especially scorching in Texas.

Austin, Texas, has reached 100 degrees or greater for 36 consecutive days in a row, while San Antonio has reached 105 degrees or more for a record seven days in a row.

Temperatures in Houston have climbed to 101 degrees or higher for a record 14 days in a row.

In the coming days, temperatures in the South will fluctuate slightly as a cold front sweeps through from the North, which will provide some relief. The cold front will lower some of the alerts in the area and bring conditions closer to normal for this time of year.

Elsewhere, temperatures are jumping into the 90s and 100s through the week ahead.

Toward the end of the month, the excessive heat from the South is expected to expand to the middle of the county, making the heat dome larger.