Firefighters across the Bay Area are on high alert as rising temperatures and strong winds fueled several blazes Wednesday in the North Bay, and officials kept an eye out for the tiny spark that could lead to disaster in the South Bay or East Bay.
A dry winter and spring led state fire officials to announce last week that this year's fire season will be unusually long and potentially dangerous.
Temperatures this week are expected to peak Thursday, hitting the 100-degree mark in some Bay Area communities and prompting some departments to increase daily staffing, post fire danger signs in regional parks and remind residents in fire-danger zones to take serious steps to protect their property.
Thursday's forecast calls for a high of 86 in downtown San Francisco; 89 in San Mateo; 92 in San Jose; 94 in Gilroy; and 95 in Livermore. Temperatures are 20 degrees higher than normal for this time of year, said Will Pi, a meteorologist with the National Weather Service.
Cal Fire officials say wildland fires are up 61 percent through the first four months of the year, caused primarily by the dry winter.
"In the last couple of days, we've seen a significant increase above what would have already been a very high number of fires this year," said Cal Fire spokesman Daniel Berlant.
On Wednesday, the heat fueled three wildfires that burned in Wine Country; a handful of minor fires were reported in Alameda and Contra Costa counties, but crews pounced on them quickly, and none caused any reported damage by Wednesday evening.
About 280 firefighters were divided between a Sonoma County fire and two others in Napa County. Crews from Alameda County Fire as well as Livermore-Pleasanton Fire, Hayward and Fremont had all been dispatched to help fight the Yellow Fire in Sonoma County.
Cal Fire has banned open residential burns in Santa Clara, Alameda, Contra Costa San Mateo, Monterey and Santa Cruz counties.
The agency, which oversees much of the state's wildfire coverage, also ramped up its seasonal firefighting staffing ahead of schedule.
"We've also increased the department's daily staffing level so we had additional firefighters and equipment ready to respond," Berlant said. "Obviously they were needed because we had a rash of fires break out overnight."
The biggest of the three North Bay blazes was the Yellow Fire, which by Wednesday had burned at least 125 acres of oak woodland and rolling hills east of Healdsburg in Knight Valley and was 50 percent contained. There were also smaller fires burning north of Napa and near the Schramsberg Vineyards, Berlant said.
The National Weather Service issued a red-flag warning for the East Bay hills and the Diablo Range beginning at 6 p.m. Tuesday -- signaling an earlier start than normal to this year's fire season in the Bay Area, a local fire marshal said.
The warning, which was set to end at noon Thursday, comes after an unseasonably dry April that caused vegetation in the area to turn brown quickly. Division Chief Jim Crawford of Cal Fire's Santa Clara County unit said the red-flag warning applied mainly to Bay Area land above 1,000 feet, where winds are higher but "dryness reaches down to the valley floor."
"There are still a lot of opportunities to have fires break out in other areas," he said.
He said that in the South Bay and East Bay areas, they've doubled engine companies from three to six and have 15 extra firefighters staffed throughout. They've also got a helicopter and bulldozers at the ready.
Crawford said this week was a transitional week for Cal Fire, with 42 extra seasonal firefighters coming in for training. He said they took an extra step to make sure those crews are ready to break away from training and join in any necessary firefighting.
Fire personnel also posted "barbecue suspension" signs in parks throughout the region this week. On Wednesday, fire danger signs were posted at Garin Regional Park in Hayward and Mt. Diablo State Park in Contra Costa County.
With fire danger peaking early in the year, fire officials are asking residents to be proactive in protecting their homes and community.
"The most important person in protecting a house from wildfire is not a firefighter, but the property owner," said Contra Costa County Fire Marshal Lewis Broschard.
Homeowners who live on the edge of open spaces are asked to maintain at least 100 feet of defensible space between their home and the wildland area. They're also being asked to avoid using power tools as much as possible.
Kristy Hubbard, who has lived next to Briones Regional Park near Martinez for more than 20 years, said fire season is "just another part of the year" but that she and her family were well prepared.
"We have never had to worry," she said with a smile as she knocked on her wood bannister."
Staff writers Eric Kurhi and Katie Nelson contributed to this report. Contact Natalie Neysa Alund at 510-293-2469. Follow her at Twitter.com/nataliealund.