The Signorello Estate winery burns in the Napa wine region in California on Monday. (Josh Edelson/AFP/Getty Images)

Adam Lee walked for miles through a wildfire-ravaged neighborhood in Santa Rosa, Calif., that looked like a “nuclear zone” to see whether his winery had withstood the huge, fast-moving wildfires sweeping through the area.

When Lee emerged from the ash and the smoke, he learned he had been lucky: Siduri Wines was one of the few buildings spared in an area of Santa Rosa decimated by fires this week. But much remains unknown about the fate of the wine industry in Napa and Sonoma counties, whose food and wine culture draws millions to its rolling vineyards each year and where vintners produce some of the best wines in America and the world.

At least four wineries in Napa have suffered total or significant losses and nine reported some damage, according to Napa Valley Vintners, a trade association. At least two wineries in Sonoma are thought to be severely affected and several hotels and restaurants are thought to have been destroyed. But with fires still burning, people still being evacuated and owners unable to access their vineyards, the full scope of the damage to the area’s fertile ground and coveted vines might not be apparent for days.

“We’re not going to know anything for quite some time because the fires are still raging,” said Margaret Bradley-Foley, owner of Petrichor Vineyards in Santa Rosa. She was out of town this weekend and has not been able to get to her vineyard, but said her neighbor’s house burned down.

Napa and Sonoma account for about 10 percent of California’s wine industry, which generates about $114 billion in annual economic activity and draws 23.6 million tourists to the state each year, according to the Wine Institute. California is the world’s fourth-largest producer of wine.

An out of control wildfire approaches Gundlach Bundschu winery on Monday in Sonoma, Calif. (Justin Sullivan/Getty Images)

But the impact of Napa and Sonoma is much larger than the numbers show. The region has become a wine and food mecca, a draw not only for wine tastings but for weddings, anniversary trips and events. The region also makes much of the nation’s high-end wine, and the fires could have a disproportionate impact on the fine-wine market, said Stephen Rannekleiv, a beverage analyst at Rabobank International.

“When you think of wine country, you think of Napa and Sonoma,” Rannekleiv said. “It’s the face of the California wine ­industry.”

The fires, which have decimated neighborhoods, charred resorts and left coils of fire snaking through vineyards, struck during harvest season. Those in the industry think the damage to grapes would have been worse any other year: About 90 percent of this year’s grapes have been harvested, far ahead of schedule.

Because of extreme heat in September, “we front-loaded harvest this year, which is atypical for us,” said Karissa Kruse, president of the Sonoma County Wine Growers. Kruse spoke on the phone outside of her home, which was destroyed in the fire.

Mary McAuley, founder of Ripe Life Wines, sources her fruit in Mendicino County, which has been ravaged by wildfires. McAuley said the county still has 20 to 30 percent of its fruit on the vine.

“No one can see, it’s smoky as hell, there’s still no power, and even if you could pick you can’t bring it in. You can’t process it,” McAuley said. It’s hard to get in touch with people there; few are worried about wine or vineyards. “They’re focused on saving lives.”

Burned out wine bottles sit on a rack at the fire-damaged Signarello Estate winery. (Justin Sullivan/Getty Images)

Kruse said many vines in Sonoma are not thought to be damaged because of their water content; instead, the brush between the vines catches fire. The worry, she said, is that structures that contain tanks of wine will burn.

But Lee, of Siduri, is concerned about his tanks. He has wrapped dry ice packs around the fermenters to make sure oxygen can’t get in, and opened doors and windows to make sure carbon monoxide from the fermenting process is aired out of the winery.

“I wouldn’t say it’s going as normal, but we should still be able to make wine out of it, and good wine, but it’s not the way we would make wine,” he said.

Patrick Llerena, who works at Locals tasting room in Geyserville, Calif., said cabernet sauvignon and zinfandel grapes probably are still on the vine and most at risk. He said the smoke is so thick that going outside for 15 minutes “is like smoking a pack of cigarettes.”

Some wineries were harvesting grapes when the fires swept in. At Carlisle Winery, a night pick was in progress when employees were told to evacuate.

“Fruit is still in bins on the ground at the vineyard,” owner Mike Officer said. “Can’t get to the fruit, as the road is closed. A lost cause at this point.”

Gerry Pasterick, the owner of Pasterick Winery in Healdsburg, said the grapes need to be picked and crushed before they over-ripen and begin to shrivel in the early autumn heat.

Even where the grapes have been picked, he said, there are wineries without power that can’t process them.

“A winery without power can’t crush and it can’t ferment,” he said. “And Mother Nature waits for no one. She does what she wants, when she wants. So you’ve got thousands of dollars worth of grapes that are going to be useless if you can’t get them into the fermenters.”

Many employees — amid the annual August to October harvest — lost their homes in Santa Rosa and won’t be able to work until they find shelter, if there’s a workplace to go to. In Sonoma, more than 90 percent of farmworkers work in vineyards.

Although the harvest was nearing its end this year, many of the thousands of workers who flock to the area were still in wine country, according to Armando Elenes, a vice president at the United Farm Workers of America, which represents about 800 farmworkers there.

Elenes said the fire presented specific challenges for farmworkers, the large majority of whom are thought to be undocumented immigrants. “With land worker wages low, any loss of work is really difficult,” he said. “The cost of living in this area is extremely expensive.”

Many of the workers will not be able to get unemployment assistance because of their immigration status, Elenes said. Those who do qualify for other services, including stays at local shelters, are more reluctant to seek government help, he said.

“A lot of workers are hesitant to get those services because they’re afraid,” he said.

About 30 farmworkers were airlifted from two vineyards on a Napa peak on Sunday. They had been working overnight shifts as the fire spread, rendering the roads around them impassible.

Ken and Melissa Moholt-Siebert were in their home on the property of Ancient Oak Cellars in Sonoma County, 31 acres where Ken’s grandparents first planted vines. A neighbor pointed out flames in the distance a little after midnight Sunday morning; Ken said the fire hooked to the north and a half-hour later the couple was choking on ash. They fled.

The couple was able to see their property from the 101 freeway on Tuesday. The pasture land appears to be destroyed, but some of the 15 acres of pinot noir grapes appear to be okay.

“It’s not as bad as it could be and it may be minimal damage, but until we’re allowed in we won’t be able to see,” Melissa Moholt-Siebert said. The couple said the winemaking community has been extremely supportive — a warehouse set up a grill and served hot dogs and steak to the community Tuesday. But she worries about what could happen in the next few days.

“The fire is not at all contained,” she said.

Nancy Light of the Wine Institute said some vineyard owners have not yet reported the condition of their vineyards, due in large part to spotty communications, and that the priority is to make sure that employees are safe.

There is concern, however, that the fires could dramatically affect tourism in Napa and Sonoma at a peak time of the year.

“The fear and concern is it’s a big time for tourism, and when people see something like this they reconsider their plans or cancel their plans, and I’d say it’s too early to do this,” she said. “We do think the industry will be able to spring back and we’ll be able to welcome tourists.”

Breena Kerr in Healdsburg, Calif., and Alice Crites and Dave McIntyre in Washington contributed to this report.