Heat Index values of 120 forecast as heat wave

The dangerous, record-smashing heat wave that’s already killed at least 14 people in Texas and Louisiana will continue Thursday across much of the southern tier of the U.S., as blistering temperatures in the 100-degree range scorch the region, along with punishing humidity.

The life-threatening heat will plague “a large portion of the nation from southeast New Mexico, through much of the Southern Plains, eastern Kansas, into the Lower Mississippi Valley, Lower Ohio Valley, Lower Tennessee Valley and the central Gulf coastal region,” the National Weather Service warned.

Many areas outside of Texas will endure their most significant heat of the season thus far on Thursday. In total, more than 110 million Americans live where a heat alert is in effect.

The worst of the heat on Thursday and over the next several days is expected in cities from Dallas to Houston, New Orleans, Jackson, Little Rock, Memphis and Nashville, where heat index values of 110 to 120 are expected. The heat index is how hot it feels to the human body when humidity is factored in. “Heat is the leading cause of weather-related deaths each year,” the weather service tweeted Wednesday. “Take it seriously.”

Here’s a look at Thursday’s forecast elsewhere in the U.S.

US heat index map

Heat wave weather forecast:Here’s how hot it will get, as 31 million face heat warnings

Heat expected to build to California interior valleys

As a mid to upper level ridge strengthens over California and the Great Basin, the golden state can expect heat to spread throughout its interior valley later this week. Most of Sacramento and San Joaquin Valleys already have excessive heat watches in place. High temperatures will reach the lower 100s going into the weekend.

Southern California, which is not yet in a heat advisory, is already grappling with wildfire season. A wildfire in San Bernardino County burned about 90 acres Wednesday while another in Riverside County burned 68 acres.

“Now, we’re going to start seeing higher temperatures, lower humidities come this weekend, and any little spark will ignite a fire,” said CAL FIRE Riverside County Fire Capt. Richard Cordova according to ABC7. “As you can see, this grass is ready to burn and we haven’t see this type of grass crop in over years because of the drought and now we’re seeing six foot grass crops out here.”

Southern California wildfire map

Canadian wildfires keeps a third of U.S. population with low air quality

With no end in sight for the Canadian wildfires, poor air quality is expected to persist as the smoke keeps spreading south. More than a third of Americans live in areas with air quality advisories and alerts, including the Upper Mississippi Valley, the Mid-West, Great Lakes, Ohio Valley and the Mid-Atlantic.

Canada has over 250 blazes burning “out of control,” according to the Canadian Interagency Forest Fire Centre, marking the nation’s most severe fire season on record. Health experts advise Americans under air quality advisories to stay indoors with air conditioning or to wear N95 masks outside.