California’s wildfire season is off to its worst start in 10 years.

Through Monday morning, 196,092 acres have burned across the state since Jan. 1 — an area seven times the size of San Francisco and more than double the average by July 9 of the previous five years — according to an analysis of federal and state fire statistics by the Bay Area News Group.

From the Oregon border to Napa County, Santa Barbara to San Diego, thousands of firefighters with helicopters, bulldozers and air tankers Monday battled hot temperatures and windy conditions at a time when, most years, summer fire season has barely begun.

The last time this much of California had burned by July 9 was in 2008, when a series of freakish dry lightning storms had burned three times as much: 627,000 acres, much of it in the remote back country of Big Sur.

The reason behind this year’s ominous early trend is something many Californians thought was behind them: the 2012-2017 drought. The relentless drought, the most severe at any time since California became a state in 1850, ended with drenching rains in the winter of 2016-2017.

But along the way the historic dry spell killed millions of shrubs, bushes and trees. They are still there. And now all that dead vegetation has dramatically increased fire risk, fire experts said Monday.

“We are going to be dealing with the impacts of that drought for many years,” said Scott McLean, deputy chief of CalFire, the state’s firefighting agency.

Add to all that dead vegetation difficult local conditions, and the fact that the winter of 2017-2018 was drier than normal in much of the state, leaving the moisture levels of plants, shrubs and trees dangerously low.

“Over the last three weeks we’ve been dealing with dry north winds, triple-digit temperatures and low humidity,” McLean said. “That adds up to perfect fire weather. It’s extremely dangerous”

High winds in Yolo County and Napa County spread the County Fire, which began June 30 and has burned 90,000 acres through Monday afternoon but now is 73 percent contained. A heat wave in recent days that sent temperatures in Los Angeles County to 115 degrees made conditions difficult for the Holiday Fire, which burned 13 homes in Goleta, in Santa Barbara County, and now is 90 percent contained.

And the combination of heat and erratic winds have hampered fire crews battling the Klamathon Fire in Siskiyou County, along Interstate 5 near the Oregon border. That blaze, at 35,250 acres, has crossed into Oregon and was just 30 percent contained Monday afternoon, having burned 81 structures with 800 still at risk.

National wildfire risk maps show the highest fire danger in the country are Northern California near the Oregon border, Central California from the Bay Area to Santa Barbara, and Northern Nevada and southern Idaho, said Craig Clements, an assistant professor of meteorology at San Jose State University.

When scientists look at the moisture content of shrubs, small trees and other plants less than half an inch in diameter, California and Nevada are bright red on national maps — the driest conditions — with many plants at only 3 or 4 percent moisture, down from 10 to 20 percent in other parts of the country.

Clements said he’s hoping cooler weather, and an especially careful public, will reduce the risk over the coming months.

“It could be a big year,” he said. “But if you don’t have the ignition, you don’t have fires.”

Typically, October has been the most dangerous fire month in California. That’s because most rain stops by April and doesn’t start again until November. As a result, by early fall, grasses, shrubs and trees are at their driest point. The 1991 Oakland Hills Fire, which killed 25 people and burned 2,900 homes, occurred in October. Last year’s Wine Country fires in Napa, Sonoma, Mendocino and other Northern California counties also began in October, killing 44 people and burning 8,900 structures. And the Cedar Fire, which killed 15 people and burned 273,000 acres in San Diego County, also burned that month.

Climate change is lengthening the fire season, said Scott Stephens, a professor of fire science at UC-Berkeley. Hotter temperatures dry out vegetation earlier in the year.

“We’re just having longer periods where fires can ignite and move,” he said.

This year, late rains in May also boosted grass in many areas by about 50 percent. Now that the weather is hot and dry, that means more material to burn.

“It looks pretty severe,” Stephens said. “I expect this will be a challenging year because of this early activity.”

The total of 196,092 acres burned in California so far this year is more than twice the average of the previous five years through July 9, which was 77,905 acres, and also far more than the average of the previous 10 years, which was 111,490 acres.

Those numbers come from the National Interagency Fire Center, in Boise, Idaho, which publishes daily reports with wildfire totals across the country, including from state agencies, the U.S. Forest Service, the National Park Service and other government land agencies.

This year’s California total is not only the second worst in the past 10 years but the second worst since 1994 when detailed daily records were first kept by the National Interagency Fire Center.

To be sure, a bad start doesn’t mean a bad finish, and vice versa. Last year at this time, only 68,647 acres had burned in California — barely one-third of this year’s total so far. But windy, dry conditions in October toppled power lines across Northern California and made it one of the worst fire seasons on record. The Wine Country fires in Napa and Sonoma counties were followed in December by the Thomas Fire, which burned 281,063 acres in Santa Barbara County — making it the largest wildfire in state history — before mudslides in the burned area killed 21 people the following month.

Some parts of the state, particularly Santa Barbara and Ventura counties, have seen so little rainfall that they never were officially removed from drought status.

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Yosemite National Park to reopen Friday, with more campsites available “Six of the last seven years in California have been in drought,” said Jessica Gardetto, a spokeswoman for the National Interagency Fire Center. “These hot and dry temperatures are going to persist, and that is compounding the problem. Once these fires start, they are incredibly difficult to put out.”