California's fourth-largest wildfire fills Yosemite Valley with smoke on holiday weekend

The Rim Fire jumps Highway 120 near Hodgdon Meadows in Yosemite National Park on Friday. Al Golub / Zuma Press

Smoke from a huge wildfire blanketed Yosemite Valley for the first time on Saturday, a blow to tourists -- and their health -- on one of the busiest weekends in one of the nation's most popular national parks.

"I'm in Yosemite Valley right now, and I cannot see the cliffs around me," park spokeswoman Kari Cobb told The Associated Press. "The wind has shifted and smoke is impacting the entire park. We have been lucky until now."

Air quality data on the park's website showed that the maximum one-hour average for particulates on Saturday, measured at the visitor center on the valley floor, was in the most unhealthy portion of the five-part scale. The air quality had improved by Saturday evening but was still rated "unhealthy for sensitive groups."

The Rim Fire broke out in the neighboring Stanislaus National Forest on Aug. 17 and burned into the northwest corner of Yosemite National Park late last week.

By Saturday afternoon, it had consumed nearly 223,000 acres, making it the fourth-largest wildfire ever in California, surpassing a 1932 fire in Ventura County. Only about a quarter of that is within the park, but National Park Service Director Jonathan Jarvis said Saturday that it still amounts to about 6 percent of Yosemite's backcountry, Reuters reported.

Jarvis said the fire is heading toward two groves of the park's famed sequoia trees, Reuters reported.

"This is not a catastrophe for Yosemite National Park," he said by phone after surveying the area, Reuters reported. "These trees are very old and it's not the first fire they've ever seen."

In a Friday image provided by the U.S. Forest Service, members of the BLM Silver State Hotshot crew perform burn operations on the southern flank of the Rim Fire in California. Mike Mcmillan / U.S. Forest Service via AP

Cobb told the AP that all campgrounds in the valley still were full Saturday morning despite the smoke, which was expected to stay through the holiday weekend.

More than 5,000 people are fighting the fire, and Jarvis estimated that state and federal agencies have spent about $54 million battling it.

Smoke grounded firefighting aircraft Saturday morning, but they were cleared to fly again later in the day. The AP noted that the fire now covers an area larger than San Francisco, Oakland and San Jose combined. It was 40 percent contained as of Saturday evening.

The cause of the fire is under investigation, but the possibility that it was started by an illegal marijuana growing operation was raised recently by a fire chief in Tuolomne County.

Todd McNeal, fire chief in the town of Twain Harte, west of Yosemite, said at an Aug. 23 community meeting that officials "know it's human caused, there’s no lightning in the area. … (We) highly suspect that it might be some sort of illicit grove, marijuana grow-type thing.”

His comments surfaced in a YouTube video of the meeting.

The San Jose Mercury News reported that in June, 15,000 marijuana plants were pulled out the forest to the south and four miles of irrigation pipe were removed. The newspaper said a 40-acre wildfire the month earlier in the same area was blamed on marijuana growers tied to Mexican drug cartels.

The Rim Fire burns at night near Yosemite National Park, California, in an undated Forest Service photo released Friday. Handout / Reuters