Fourth of July forecast calls for extreme heat for most of US

The Fourth of July holiday is stacking up to be a scorcher for most of the nation.

Numerous record temperatures are expected to be broken as highs in California are forecast to stay in the triple digits through Independence Day and beyond, and hot, humid weather down South will make some places like New Orleans feel close to 120 degrees.

California, particularly cities in the San Joaquin Valley, is expected to see temperatures soar past the 110 mark for multiple days this week.

In Palm Springs, thermometers could reach 115 degrees, and similar temperatures are expected for neighboring states Arizona and Nevada.

Both Las Vegas and Phoenix are forecast to hit 115 around the holiday.

Factoring in the heat index, the nation's southern states are forecast to endure hot, sticky weather through this week. The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature, according to the National Weather Service.

On Sunday, an excessive heat warning was issued for the Lower Mississippi River Valley, where the heat index could reach up to 118 degrees. New Orleans is facing a heat index of up to 118 both on Sunday and Monday.

Heat advisories are in effect for much of the East Coast, as well. In the Carolinas, the heat index will make it feel like 110 on Sunday, while Virginia will feel like 108, and in Philadelphia and central New Jersey, the heat index will be around 103 on Sunday.

Meanwhile, hot weather up and down the East Coast is expected to give way to severe weather Sunday.

More than 60 million people along the Eastern Seaboard from North Carolina to Maine are expected to be in the storm zone Sunday afternoon.

The East Coast storms are forecast to form under hot and humid conditions. The strongest storms are expected to arrive between 2 p.m. and 11 p.m. ET on Sunday.