(CNN) — Residents in parts of Arizona were ordered to evacuate Sunday as firefighters battled multiple wildfires across the state with extreme temperatures that have lingered for weeks.

About 160 residents were ordered to evacuate Sunday from the Sunflower area of Maricopa County because of a wildfire in the Tonto National Forest, authorities said.

Deputies were evacuating residents and advising them to head to the city of Fountain Hills, where an evacuation center has been set up, Maricopa County Sheriff’s Office Sgt. Joaquín Enríquez told CNN Sunday night.

“At this point, the fire is burning at the location and crews will monitor and continue to put out fires overnight,” said Ron Coleman, Maricopa County Emergency Management spokesman. “Additional fire suppression will continue in the morning.”

The Diamond Wildfire has burned more than 1,000 acres in Arizona
Arizona
The planes support the containment of forest fires in southeastern Arizona. (Credit: Rich Jones/AZ State Forest Area/Twitter)

Sunflower is about 95 km northeast of Phoenix, which hit 24 straight days of temperatures of 43 degrees Celsius or higher, according to a tweet from the National Weather Service. The city saw a maximum of 45 degrees Celsius this Sunday.

More than 100 miles away in Yavapai County, where six active wildfires were burning, residents of the Cherry community were also ordered to leave their homes Sunday.

“The RACETRACK fire is threatening your area. Evacuate now,” the Yavapai County Sheriff’s Office said in an “initiation message” to residents Sunday night.

A special weather declaration was in effect for parts of Yavapai County for wind gusts up to 50 mph Sunday, and the National Weather Service had warned residents to expect “wind changes for the Grapevine and Race Track fires.”

The fires come amid Arizona’s multi-week battle against extreme heat, with excessive heat warnings in much of the central and southern part of the state on Sunday.

There have been at least 18 confirmed heat-related deaths recorded in Maricopa County so far this year, as of the second week of July, with another 69 cases under investigation, according to data from the Maricopa County Department of Public Health.

The dangerously high temperatures are also affecting county hospitals, as people suffering from heat-related illnesses seek treatment, CNN previously reported.

Maricopa County, where Phoenix is located, is the fourth largest county in the country in terms of population size, according to the county’s website.

At least 44 million people were under heat advisories and excessive heat warnings as of Sunday across much of the desert southwest, the Intermountain West, south Texas and south Florida, according to the US National Weather Service.

More than two dozen records were set or tied Saturday in cities across Arizona, California, Florida, Idaho, Montana, Nevada, Puerto Rico and Texas.

Shocking images of a forest fire in Arizona 1:05
It’s so hot in Arizona that doctors are treating a large number of patients who suffered burns from falling to the ground.
Meanwhile, in Maricopa, Arizona, it’s so hot that people have been transported to the emergency room with major, sometimes life-threatening burns. During the last three to four weeks of this record-breaking heat wave, people have been burned just by falling to the ground.

“Summers are our peak season, so we anticipate that these kinds of things are going to happen. But this is really unusual — the number of patients that we’re seeing and the severity of the injuries, the acuity of the injuries is much higher,” said Dr. Kevin Foster, director of Burn Services at the Arizona Burn Center at Valleywise Health. “The numbers are higher and the severity of the injuries are higher, and we don’t have a good explanation for it.”

Every one of the 45 beds at the burn center is full, he said, and a third of the patients are people who fell and burned themselves on the floor. There are also burn patients in the ICU, and about half of those patients are people burned after falls.

“It has definitely taken its toll,” Foster said.

The area has been hotter than normal, even for Arizona, and that, experts say, means the ground can be dangerous to anyone whose bare skin comes in contact with it.

Asphalt is dark and dense, while concrete is lighter and reflective.