LOS ANGELES (AP) — Timber and brush parched from a years-long dry spell and thick grass that grew after drought-busting winter downpours are making for early and unpredictable wildfire behavior that California officials haven’t seen for years, if at all.
Dense layers of new grass are providing a “fine fuel” for flames that then gain speed and intensity by moving through “standing dead fuel” made up of vegetation and trees that shriveled during the state’s six-year drought, said Kathleen Schori with the California Department of Forestry and Fire Protection.
“It’s difficult to remember a year quite like this one,” she said Tuesday. “There’s such a mix of fuels that these large damaging fires are starting at least a month earlier than usual.” The result, she said, could be a longer and more destructive fire season than California has experienced in a while.
Authorities surveying the damage from a blaze in Northern California said Tuesday that at least 41 homes and 55 other buildings had been destroyed near the town of Oroville, about 150 miles (241 kilometers) northeast of San Francisco.
Residents had started to return home after fleeing a wildfire in the grassy foothills of the Sierra Nevada, about 60 miles north of Sacramento, but at least 4,000 were still evacuated. The blaze burned nearly 9 square miles and injured four firefighters. It was partially contained.
Schori said this year’s conditions were similar to California’s 1979 wildfire season, which came on the heels of a two-year dry spell and saw blazes blackening a total of 386 square miles of grass, brush and timber and caused more than $30 million in damage.  However that year’s major fires didn’t kick off until well into August, she said, as did the destructive 1992 blazes that followed a drought that started five years earlier.
Major downpours last winter pulled the state out of years of drought but also brought a layer of grass that early-summer fires are greedily feeding on.
“That creates faster moving fires, hotter fires, it carries fire much more readily,” said Santa Barbara County fire Capt. Dave Zaniboni, whose department was battling two large wildfires.
Older, dried out trees and vegetation are especially dangerous for wildland blazes, but enough new and drying grass can provide links between such tinderboxes.
With the dense grass as the “carrier,” the firefight becomes much more challenging because “you have to make sure the water is getting all the way down to the smoldering areas below,” Schori said.  “It takes a lot more effort to extinguish grass fires.”
Three new fires forced evacuations on Tuesday.
One of them, just east of San Jose, destroyed two structures, at least one of them a home.
Another broke out in San Diego County about 2 p.m. and quickly surged to over half a square mile. It forced the closure of Interstate 8 and the evacuation of five homes in Alpine, a town of 15,000 people about 50 miles northeast of San Diego.
In Northern California, the Placer County Sheriff’s Office has issued mandatory evacuations along four roads near a 2-acre fire burning north of Auburn.
In Southern California’s Santa Barbara County, at least 3,500 people remained out of their homes due to a pair of fires. The larger of the two charred more than 45 square miles of dry brush and has burned 20 structures since it broke out. It was 45 percent contained. To the south a 17-square-mile wildfire that destroyed 20 structures is 25 percent contained.