Maps show heat alerts as extreme temperatures threaten millions

▶ Watch Video: Millions of Americans under heat alerts

Roughly 100 million people across the United States are facing extreme temperatures this week as a heat dome scorching the western part of the country spreads to the Northeast. 

In Billings, Montana, temperatures reached a record high of 111 degrees on Sunday as the dangerous heat was felt across the Great Basin, the Rockies and sections of the desert Southwest. 

Maps show latest heat wave

Temperatures are forecast to be 20 to 30 degrees above average for this time of year, according to CBS News meteorologist Nikki Nolan. Some locations will see record-breaking temperatures through the week.

The peak for the Northern Tier is expected on Tuesday, while the Northeast’s peak is expected on Wednesday. The heat index across this wide stretch of the country will reach into the high 90s to over 100 for the next several days.

Salt Lake City reached an all-time high on Sunday, with temperatures reaching 109 degrees, according to the National Weather Service. The previous record was 107 degrees, which was last broken in 1960, 2002, 2021 and twice in 2022. Most of Utah was under an extreme heat warning, which was scheduled to remain in place through Tuesday morning.

Heat also spread across the Dakotas, with forecasters issuing extreme heat warnings for vast sections of both states. 

Forecasters warned of the dangers associated with the unusually prolonged bout of heat, which they’ve called “exceptionally rare” for some locations, even in mid-July. The National Weather Service said hazardous heat would spread eastward at times, while lingering in that central region through next weekend.

The heat dome — an atmospheric phenomenon that essentially traps hot air over a particular location —  built in the West after the first heat wave of the summer began to bake the area last week. Now, forecasters said people should brace for widespread temperature highs between 105 and 115 degrees, breaking numerous local temperature records and increasing wildfire risks. They also warned about the heightened chance of heat-related illnesses, including heat stroke.

“Extremely hot daytime highs combined with potentially record-warm lows will result in increasing heat stress over the next several days due to limited relief,” the weather service said in an advisory.

Heat fuels wildfires, fires up thunderstorms

In California, the Summit Fire in the Antelope Valley temporarily forced people outside Los Angeles to evacuate as it burned nearly 3,000 acres. The Los Angeles County Fire Department said crews made significant progress on the blaze, with containment at 31% as of Sunday evening, CBS Los Angeles reported.

Extreme heat is expected over parts of Southern California and into Arizona through Thursday, according to Nolan. Temperatures are forecast to reach into the 90s and 100s, especially in the desert Southwest.  Overnight temperatures were forecast to be record-breaking in Southern California, but the Southwest wasn’t expected to break records, Nolan said.

Two wildfires were sparked on Sunday in Colorado’s high country even as firefighters continued to battle the Aspen Acres Fire, which had burned more than 850 structures, including hundreds of homes.

Sen. John Hickenlooper, a Colorado Democrat, toured the damage this week and said the state needs more funding to battle wildfires.

“There have been huge cuts to the fire service, to the BLM [Bureau of Land Management], there’ve been cuts everywhere,” Hickenlooper said.

Rain and flood risk 

Heavy rain storms and flooding are a concern in parts of the South. In Louisiana, thunderstorms dumped several inches of rain on New Orleans, forcing families to wade through knee-high water. 

Also on Saturday, hundreds of people were rescued amid historic flash flooding in Missouri. Rescue crews airlifted more than 200 people stuck at a children’s camp after 6 to 12 inches of rain fell in the southeastern part of the state.

Farther east, communities in the Philadelphia area were cleaning up after powerful microbursts ripped through neighborhoods with gusts up to 70 miles per hour.  Mayor Cherelle Parker signed a Declaration of Disaster Emergency on Sunday, CBS Philadelphia reported.