A dangerous heat wave spanning 21 states as of Wednesday morning has sparked wildfires across the Western United States and put over 110 million people under heat watches, warnings and advisories, the National Weather Service warned.

This Fourth of July week will be a “scorcher across much of the West and from the southern Plains to the Mid-Atlantic,” the NWS said Wednesday morning.

The excessive heat wave broiling much of the West is expected to continue into next week, expanding into the Pacific Northwest and the Intermountain West by the end of the week.

California wildfires prompt evacuations

Temperatures are expected to reach triple digits in the range of 105-115 degrees Fahrenheit throughout California, where multiple wildfires sparked at least nine wildfires as of Tuesday night, according to the Los Angeles Times.

A wildfire that spread into residential areas in Oroville, California, prompted Gov. Gavin Newsom to declare a state of emergency in Butte County Wednesday, with 13,000 people being under an evacuation order, as the Deseret News reported.

Triple-digit temperatures in Utah

Temperatures are expected to rise to dangerous levels in Utah after the Fourth of July and heading into next week, with areas of the state possibly reaching triple digits.

“High pressure building along the West Coast this week will produce a warming trend across much of the Western U.S.,” NWS Salt Lake City explained. “As this high pressure shifts eastward, the potential for dangerous, record-breaking heat increases across Utah and southwest Wyoming heading into next weekend and likely continuing into next week.”

Temperatures over 100 degrees Fahrenheit along the Wasatch Front and 110 in the St. George metro area are expected next week.

Staying safe in a heat wave

The National Weather Service warned that the duration of the heat wave into next week is particularly dangerous because “heat impacts can compound over time.”

Avoid heat stroke, dehydration and more by “staying hydrated, out of direct sunlight, and in buildings with sufficient air-conditioning,” per the NWS. “It is also very important to check on the safety of vulnerable friends, family, and neighbors.”