The National Park Service says Sequoia and Kings Canyon National Parks are experiencing much higher numbers of visitors than usual because of closures at Yosemite National Park.
The blaze, known as the Ferguson Fire, has burned for roughly two weeks and encroached on the western boundary of the park, sending smoke into the Yosemite Valley where numerous park's most famous attractions are located.
Jerry Brown on Thursday issued emergency proclamations in both Riverside County in the south and Shasta County in the north.
The Ferguson Fire, which started on July 13 in the Sierra Nevada mountains, has destroyed 36,500 acres (14,800 hectares) of vegetation, according to InciWeb, the Forestry Service's incident information website.
Yosemite Valley will be closed until at least Sunday, along with a winding, mountainous, 20-mile stretch of California's Highway 41 that leads into the area, park spokesman Scott Gediman said.
In the Sierra Nevada, famed Yosemite National Park was closed as smoke from a fire to the west cast a pall on the region.
Climbers from a group that had rappelled down El Capitan pack up after rangers asked them to leave Yosemite National Park in California owing to a nearby fire on July 25, 2018.
The scenery at Yosemite has been blanketed in hazy smoke, as seen on the park's webcams, at the height of the summer season when the park is swarming with visitors.
The National Park Service (NPS) posted the news Tuesday, confirming that both the Yosemite Valley and Wawona - which comprise of almost 8,000 acres - would be closed to visitors as of 12 p.m. on Wednesday, July 25. It was burning in and around San Bernardino National Forest, prompting officials to order evacuations for Idyllwild and surrounding communities, which are home to about 12,000 people.
Yosemite Valley closed to battle wildfires
This has resulted in at least 1,000 campground and hotel bookings being cancelled.
Heavy smoke from the 60-square-mile (155-square-kilometer) fire is hanging over the valley, which normally bustles with summer visitors.
Backfiring is the process by which firefighters burn fuel in the path of a wildfire in order to either redirect the fire or to keep it from spreading.
Park workers were offered air purifiers and the government set up "clean rooms" to provide respite to people affected by the smoke.
Over almost two weeks, the blaze has churned through more than 38,000 acres of timber in steep terrain of the Sierra Nevada just west of the park.
Authorities ordered residents to leave Idyllwild and several neighboring communities, home to about 12,000 people.
More than 3,400 personnel are involved in fighting the blaze, NWCG says, in the operation that includes "220 engines, 47 water tenders, 16 helicopters, 88 crews, and 59 dozers".
The new evacuations cover communities outside the park's north side.
Almost 700 firefighters were battling the conflagration, which had charred 4,700 acres (1,900 hectares) and was only 5 percent contained as of Thursday afternoon.More news: Zimbabweans React to Robert Mugabe's Surprise Press Conference