By Melissa Alonso and Robert Shackelford, CNN

(CNN) — Thousands of people have been ordered to evacuate in Northern California due to a wildfire raging in Butte County, as an “exceptionally dangerous and deadly” heat wave intensifies in the West.

Rising temperatures – which will continue into next week – have dried out already arid vegetation, increasing the risk of forest fires in the region.

Governor Gavin Newsom declared a state of emergency for the area where the fire was burning, allowing for additional resources, including the ability to mobilize the California National Guard in support.

The governor’s proclamation estimates the size of the fire at about 4,000 acres and cites “persistent high temperatures throughout the day and night, dry conditions, and strong winds” that have increased the intensity and spread of the fire.

A local state of emergency was also declared and some residents in the city of Oroville were ordered to evacuate Tuesday night as the Thompson Fire continues to burn in Butte County, local officials said.

Cal Fire reported in an update early Wednesday morning that the fire was zero percent contained.

Four firefighters battling the blaze were injured, Cal Fire said. More than 1,400 firefighters are battling the flames, along with eight helicopters and numerous firefighting aircraft, the agency said.

Oroville is located about 65 miles north of Sacramento and has a population of about 15,000. The city is about 20 miles south of Paradise, where the disastrous Camp Fire in 2018 killed more than 70 people. Some residents affected by that fire eventually moved to Oroville.

About 13,000 residents of communities east of Lake Oroville were ordered to evacuate, according to the Butte County Sheriff’s Office.

Red flag warnings are in effect across the west, including the fire zone, due to extreme heat, gusty winds and low humidity. The already high temperatures are set to increase on Wednesday as an exceptionally long heat wave begins.

The Basin Fire in Fresno County has burned more than 13,000 acres and is currently only 26% contained.

“Outdoor lighting and especially fireworks is discouraged,” the weather service in San Francisco warned ahead of the Fourth of July holiday.

More than 85 million people in parts of the south-central and western US are under heat warnings this week.

The heat wave is “exceptionally dangerous and deadly,” the weather service in San Francisco said, warning that “an event of this magnitude, scope and duration would likely rival anything we have seen inland in the past 18 years.”

The heat set in on Tuesday in parts of the West, where numerous daily records for highest temperatures were tied or broken:

  • Ukiah, California: 110 degrees (tied with old record set in 1924 and 2013)
  • Concord Airport, California: 107 degrees (old record 104 degrees, set in 2001)
  • Santa Rosa, California Airport: 106 degrees (old record 101 degrees, set in 2001)
  • Napa Airport, California: 102 degrees (old record 101, set in 2001)
  • San Jose, California: 102 degrees (tying the old record, set in 1970)

In some cities, it can be hot for days with temperatures well above 38 degrees Celsius. In Sacramento, California, it can even be over 40 degrees Celsius for a whole week.

Most of California outside the immediate coastline is under extreme heat warnings, with high temperatures in the upper 90s and as high as 115 degrees possible.

Las Vegas could see temperatures of over 110 degrees Celsius all week. The current record is 10 consecutive days set last year. Death Valley could see temperatures of 120 degrees Celsius or higher all week.

The heat is expected to spread into the Northwest and parts of Arizona, including Phoenix, over the weekend, with temperatures expected to top 230 degrees, with highs of over 110 degrees in some parts of Arizona.

A 10-year-old child died Tuesday in Arizona after experiencing a heat-related emergency while hiking with family at South Mountain Park and Preserve, authorities said. First responders performed an active mountain rescue and airlifted the child to a hospital, where he later died, Phoenix police said.

A 69-year-old hiker from Austin, Texas, died Saturday in the Grand Canyon, the National Park Service said. Scott Sims lost consciousness on the trail, and attempts by bystanders and paramedics to revive him were unsuccessful.

Park rangers warn that temperatures on the trail can reach over 120 degrees Fahrenheit in the shade in the summer. They advise against hiking during daylight hours, between 10 a.m. and 4 p.m. The rangers say that assistance to hikers may be delayed in the summer due to increased demand and limited resources.

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CNN’s Amanda Musa, Lauren Mascarenhas and Cheri Mossburg contributed to this report.