The green is disappearing from South Bay hills earlier than usual this year, and fire officials say that's a red flag for a potentially long and busy wildfire season -- a dangerous scenario that mirrors the rest of the state.

State officials issued a warning this week that a lack of rainfall has left much of California's wild lands ripe to burn. Already, Cal Fire has responded to 680 wildfires across the state -- more than 200 above the average for this time of year.

While the East Bay has seen a number of fires break out in the hills near Dublin and Livermore, Cal Fire spokesman Daniel Berlant said they haven't yet seen such activity in the South Bay.

But he stressed the potential is there: Current conditions are setting the stage for a season even drier than that of 2008's Summit fire, which in May 2008 consumed 4,270 acres and 99 structures in the Santa Cruz Mountains; or 2007's Lick fire, which blackened more than 47,000 acres of Henry W. Coe State Park.

"For how dry the grass is at this time, in some areas it looks a month to two months early," Berlant said. "Already we're starting to see the grass turn brown and dry out, and what's helped that is the wind."

The yellow and brown weeds catch easier and spread faster -- green grass is filled with moisture that won't burn with the same intensity.

A 2010 Mercury News analysis of rainfall's effect on fire season found that 12 of the state's 15 worst fire seasons dating back to 1970 happened after winters that saw less rain than usual.

San Jose is currently at 66 percent of rainfall that's normally seen, with little more expected.

Eric Boldt, warning coordination meteorologist with the National Weather Service, said the state is unlikely to see any significant precipitation until fall.

"It doesn't look promising," he said.

Southern California has fared worse than the Bay Area, with Irvine at 37 percent and Riverside at 34 percent of normal.

There, Cal Fire has already increased staffing and readied the airtankers after several large early-season wildfires. A fire in the foothills northeast of Los Angeles prompted the evacuation of about 200 homes last weekend. And a 170-acre wildfire earlier this month burned two houses and threatened 160 others in Ventura County.

According to Cal Fire director Chief Ken Pimlott, in other areas they are beginning to train their seasonal firefighters -- staff that supplements the permanent crews.

In Santa Clara County and the East Bay, training will begin next week, Berlant said. He said statewide they have about 4,700 permanent firefighters who are augmented with 2,400 seasonal crew members.

Berlant said they will also be "looking very closely in May whether we need an air tanker" in the South Bay, although a firefighting helicopter is already in position near the border of Santa Clara and Santa Cruz counties.

He noted that 95 percent of fires are caused by humans. That can be due to a carelessly discarded cigarette, improper tending of a campfire or one of the most common causes -- people trying to clear land of dead vegetation with a mower or other powered equipment.

"The metal blade can spark a rock and start a wildfire, when they're trying to do the right thing," he said. "We want them to start clearing around their home now, in the springtime, while things are still relatively cooler. Do it now before things are completely dry."

The Associated Press contributed to this report. Contact Eric Kurhi at 408-920-5852. Follow him at Twitter.com/erickurhi.