FRESNO, Calif. — California’s raging wildfires have created a smoky haze so stifling that doctors in the state’s landlocked farm country say their waiting rooms have been crowding with patients struggling to breathe amid the soot-laden air.

Even without the blazes, the farming towns and subdivisions dotting the long, flat San Joaquin Valley are typically shrouded in a layer of smog during the summer.

But airborne ash from the hundreds of lightning-sparked fires caused such a spike in air pollution over the weekend that a meteorologist, Shawn Ferreria, said it took his breath away.

“I went and bought a mask because my lungs were not happy with me,” Mr. Ferreria, a senior air quality specialist for the San Joaquin Valley Air Pollution Control District, said. “What we are experiencing is way out of historical norms. I thought if I’m going to continue riding my bike to work, I better take an extra measure.”

Hundreds of firefighters were working overtime yesterday to beat back blazes burning from the western edge of the Sierra Nevada to coastal mountains near Big Sur, where authorities enforced new, mandatory evacuations along a roughly 15-mile stretch of Highway 1.

Governor Schwarzenegger deployed 200 National Guard troops to fire lines yesterday to relieve weary crews, U.S. Forest Service officials said.

Officials had hoped a fog bank along the Northern California coast would aid firefighting efforts, but the moisture did not extend inland, a meteorologist with the National Weather Service in Monterey, Brian Tentinger, said.

Even as crews made headway against some of the worst blazes, air district officials in the Central Valley grew concerned that wind patterns would send more smoke billowing into the valley, which is bordered on three sides by mountains.