Yosemite National Park will close for several days due to heavy smoke, parks officials announced Thursday afternoon.

There are no major fires burning inside the park. But because of dense smoke and the risks it poses to human health, all park entrance stations and roads closed beginning at 5 pm Thursday to vehicles and all visitors.

The park is expected to be closed at least through the weekend, said Jamie Richards, a Yosemite National Park spokeswoman.

“When you look outside at Glacier Point the view is significantly obscured,” Richards said. “You can’t see Half Dome from Glacier point, or it is very hazy. In Yosemite Valley you don’t clearly see the cliff walls.”

Parks leaders will monitor air quality and fire activity around Northern California. Campers and hotel guests with reservations have been notified and will receive refunds.

Earlier this week Sequoia National Park, located south of Yosemite in the Sierras, closed due to smoke levels and fire danger. Kings Canyon National Park remains open.

The Creek Fire, burning between Yosemite and Kings Canyon near Shaver Lake in rural Fresno County, has blackened  244,746 acres and sent smoke across the region. It was 18% contained on Thursday.

Two years ago, Yosemite Valley and the Wawona area on the park’s southern edges closed from July 25 to August 10 due to the Ferguson Fire. That fire burned 96,901 acres, killed two firefighters and injured 19 others. Investigators said it was started by an overheated catalytic converter from a vehicle that was parked over dry grass along Highway 140 outside the park.

The smoky conditions that visitors and employees are experiencing were measured as a shockingly high 785 Thursday afternoon in Yosemite Valley on the U.S. Environmental Protection Agency’s Air Quality Index scale. Anything over 150 is considered unhealthy. The levels at El Portal and Tuolumne Meadows were 588 and 540.

Anything above 300 is described on the scale as “Health warning of emergency conditions: Everyone is more likely to be affected.”

“As you are out walking around you can smell smoke in the air,”  Richards said. “You can certainly feel the impacts — the irritation in your eyes and as you breathe.”

Yosemite National Park’s famed Tunnel View, top, during a typical day, and how it looks on Thursday Sept. 17, 2020, bottom. (Top photo: Bay Area News Group Archives, bottom photo: National Park Service)