Alan Riquelmy

SACRAMENTO, Calif. (CN) — It’s not supposed to get this hot in Northern California.

Sacramento, about 90 miles northeast of San Francisco, is used to summertime highs in the mid-90s. Redding, some 160 miles north of Sacramento, gets highs around 100.

The mercury has been hitting, and on some days topping, 110 during the past week.

“We don’t ever consider that normal,” said Katrina Hand, a meteorologist with the National Weather Service.

The cause of the extended heat wave, which is expected to last through this week, is a high-pressure system lingering over the region. Essentially, it’s a mass of hot air that’s parked and isn’t forecast to start moving away for several more days.

The heat wave has played a role in this year’s fire season. It’s dry and hot, and fire fuels — which include fallen trees, branches and grass — are dried out. That can lead to them igniting easier and fire spreading faster. While the delta breeze is common this time of year in the northern San Joaquin and southern Sacramento valleys, the high-pressure system is affecting it as well.

“We are lacking that wind component,” Hand said.

Firefighters from multiple agencies have been battling blazes during the heat wave. Large fires include the Shelly Fire in Siskiyou County, which started on Wednesday and had reached almost 3,400 acres by Monday. It was zero percent contained.

The North Fire in Modoc County started Sunday. It had climbed to almost 4,400 acres by Monday and was 45% contained.

The Thompson Fire, which started this past Tuesday in Butte County, had reached close to 3,800 acres. It was 98% contained.

Further south, the Lake Fire in Santa Barbara County started Friday. It has burned over 20,000 acres and was 8% contained on Monday.

Despite being smaller, the Royal Fire in the Tahoe National Forest drew attention Sunday when it was reported that 13 hikers were somewhere within the fire zone. It's consumed almost 170 acres as of Monday and is zero percent contained.

A search-and-rescue team found the hikers outside the fire area Monday morning, said Lauren Faulkenberry, public information officer with the U.S. Forest Service.

“They are hiking back as we speak,” Faulkenberry said around 1:30 p.m. Monday. “They have yet to arrive.”

The Royal Fire is in a remote, rugged area of the national forest frequented by backpackers. There have been no reports of injuries or any damage to structures. However, the Placer County Sheriff’s Office had an evacuation warning for The Cedars, a remote community. It also evacuated park trails, which remained closed Monday, Faulkenberry said.

“The fire has continued to hold, so that’s good news,” Faulkenberry said.

Smoke from the blaze, though not flames, is visible from Interstate 80, which spans the Sierra and connects Sacramento to Reno, Nevada.

Faulkenberry advised anyone traveling to the area to first check the air quality at The air quality for the area of the Royal Fire, as well as a majority of the Sacramento region, was moderate on Monday. People with an unusual sensitivity to particle pollution were advised to reduce outdoor activities or shorten their time outside.

Hand, the meteorologist, advised people to always watch the forecast, as extreme heat can take a toll. People should use their air conditioning or visit a cooling shelter. They should also stay hydrated and avoid going outside during the hottest part of the day.

Temperatures in the Sacramento area will stay hot for several more days.

Highs will hover near 100 on Tuesday before climbing to 106 on Wednesday and 110 on Thursday. A slight cooldown will start Friday, when highs will reach 106, followed by 100 on Saturday. It appears that Sunday will be the coolest day, when highs will only get to 95.

The mass of hot air has shattered temperature records across California. The world's hottest place — Death Valley National Park — saw the mercury hit 129 degrees on both Saturday and Sunday. A motorcyclist visiting the park died of heat exposure Saturday and another was hospitalized with heat-related illness, while the other four members of their group also received medical attention.

Death Valley has reached or exceeded 125 degrees every day since July 4 and is expected to see similar temperatures through at least Saturday.

“While this is a very exciting time to experience potential world record-setting temperatures in Death Valley, we encourage visitors to choose their activities carefully, avoiding prolonged periods of time outside of an air-conditioned vehicle or building when temperatures are this high,” park Superintendent Mike Reynolds said in a statement.