A tree ignites as firefighters attempt to stop flames from the Pawnee fire from jumping across highway 20 near Clearlake Oaks, California on July 1, 2018.

There's no relief in sight for stubborn wildfires flaring all over the Western U.S., including one that began Saturday in northern California that forced the evacuation of hundreds of people northwest of Sacramento.

The National Weather Service also warned Monday in a tweet about a "very dangerous heat wave with elevated to potentially critical fire weather conditions" that is forecast later this week and into the weekend in portions of southern and central California. It forecast triple-digit temperatures in several areas on Friday and Saturday across several California counties, including portions of Los Angeles.

Heading into the Fourth of July holiday, authorities are preparing for even greater risk of wildfires due to illegal fireworks or campfires. Several fire agencies across the Western U.S. plan to have extra equipment and crews on standby through the holiday to quickly respond to wildfires.

Also, several cities and counties have banned personal fireworks due to the increased fire danger, including Mesa County, Colorado, where fines for violations can run up to $1,000 and result in a felony charge.

"Nationally, nearly nine out of 10 wildfires are human-caused, and fireworks definitely play a role in the number of human-caused wildfires," said Jennifer Jones, a spokesperson for the U.S. Forest Service.

She said firefighters are well aware of "the potential for wildfires as the forecast indicates continued hot dry weather across the region, and people will be recreating on public lands during the Independence Day holiday. The Forest Service is working with its interagency partners to be prepared for potential increases in the fire activity by strategically staging smokejumpers, engines, crews and equipment to reduce response time."

As of Monday, about 60 wildfires burned throughout the U.S. on more than 504,000 acres of federal, state and private land, according to the National Interagency Fire Center. That is up about 25 percent in terms of acreage from a year ago.

In California, at least 10 wildfires are burning throughout the state.

"Right now we're over 300 fires more than we had at this time last year in California," said Cal Fire Battalion Chief Lucas Spellman. "We just didn't stop from last year, when we even had big fires in December."

Last December's Thomas fire in southern California scorched more than 281,000 acres, a record for the state.

The largest blaze at present in the Golden State is the so-called County fire that began Saturday and as of Monday afternoon had exploded to 60,000 acres, according to Cal Fire. More than 2,115 crews are battling the blaze in three counties, Yolo, Napa and Lake, all now back in drought conditions.

The fast-moving County fire, fueled primarily by tall grass and brush, was 5 percent contained as of Monday afternoon. There's also the nearly 15,000-acre Pawnee fire burning about 40 miles away in Lake County. It started June 23 and so far has destroyed 22 structures and threatens 50 structures. As of Monday, Pawnee was 75 percent contained.

"More land has already burned in California in the first six months of this year than during the same period last year," California Gov. Jerry Brown said in a release late Monday. "Cal Fire has already fought more than 53,000 acres of wildfire this year compared to an average of 23,000 acres over the same time in previous years.

Brown also issued a statement with legislative leaders on the formation of a wildlife preparedness and response conference committee and plans to amend legislation to "help prepare the state to deal with the increasingly extreme weather and natural disasters caused by climate change."

Meantime, at least eight wildfires are burning across Colorado and six in Utah. Crews also are battling blazes in eastern Washington and southwest Oregon.

One of the largest wildfires burning in the West is the Spring Creek fire in southern Colorado, which has charred more than 56,000 acres and as of Monday morning was 5 percent contained. Authorities believe the blaze was human-caused and Saturday announced on Facebook a Danish man had been arrested and was being held on arson charges.

The so-called 416 fire outside Durango, Colorado, has burned more than 49,000 acres. It started June 1 and was 37 percent contained as of Monday.

So far this year, a total of 29,111 wildfires have burned a total of 2,534,701 acres of federal, state and private land nationwide, according to the NIFC. That exceeds the 10-year average number of acres of 2,285,234 burned by this date but lags in the number of fires.

Fire experts see continued danger of major wildfires throughout the summer due to heat, dry conditions and millions of dead trees that provide added fuel for large blazes. In California alone, the Forest Service estimates there are about 129 million dead trees on nearly 9 million acres of land. Most of the dead trees are in the central and southern Sierra Nevada region of California, and insect attacks and drought are to blame for the high numbers.

-Updated with wildfire information provided late Monday by California Gov. Jerry Brown's office.