Little more than a week ago, Signorello Estate winemaker Pierre Birebent was preparing for the start of the busiest tourist season in Napa Valley. Signorello, a Canadian-owned family winery on Napa Valley's Silverado Trail, was booked up with reservations through December, available by appointment only to roughly 4,000 visitors a year who come from around the world for private wine and food pairings and tours of the vineyards on custom-made carts.

Instead, Mr. Birebent spent Sunday night desperately trying to wet down the estate's main buildings to slow the fire that roared down the hillside to the north in a firestorm so fast it knocked over trees on the property and so hot it melted wine bottles. The thick black smoke ultimately proved too overwhelming for the winery employees, who were forced to flee the area.

Rather than showing visitors around the vineyards he has tended for the past 20 years, Mr. Birebent spent the start of this week leading insurance adjusters through the ruins of the 40-year-old winery. The estate's buildings were almost all destroyed by the deadly wildfires that swept through Northern California, killing 41 people, destroying 5,700 homes and businesses, forcing two hospitals to shut down and damaging dozens of wineries in the heart of California's wine country.

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The fires tore an uneven path of destruction through the region, incinerating winery buildings even as they left vineyards intact, levelling some neighbourhoods even as they left nearby streets unscathed. By Tuesday, the 11,000 or so firefighters brought in from across the country had largely contained the blazes near Napa and Sonoma but were facing a new set of fires near Santa Cruz, forcing the evacuation of 150 homes, as well as a blaze that broke out in the mountains north of Los Angeles.

As wineries such as Signorello grapple with how to rebuild, California's wine country is still taking stock of the economic damage. More than 97,000 hectares of Napa, Sonoma and several other counties were scorched, shutting down almost 100 hotels, restaurants, wineries and tourist attractions and forcing almost 100,000 residents to flee their homes.

For many wineries, at least the early signs are positive. Of the almost 2,000 licensed wineries and wine cellars in the region, fewer than two dozen sustained serious damage and only a handful lost grapevines.

The destruction could have been far worse. October is typically harvest season in Napa and Sonoma, but a September heatwave forced most wineries to pick their grapes early. The Napa Valley Vintners association, a trade group, estimated that 90 per cent of the grapes in the region had already been picked before the fires broke out on Oct. 8.

For the remaining unharvested grapes – mainly thick-skinned cabernet sauvignon that finds its way into some of the region's most expensive wines – the biggest risk is smoke taint, a chemical reaction on the skin of grapes that can cause wine to taste smoky. Depending on how much of the unharvested supply is affected, the fire damage could push up prices for high-end Napa 2017 cabernet sauvignon wines by 50 per cent, according to an analysis by the University of California at Davis College of Agricultural and Environmental Sciences.

At wineries such as Signorello, the green, moist vines acted like firebreaks, stopping the flames from continuing down the hillside onto the vineyards that line the valley floor. "The vineyard doesn't really burn easily," Mr. Birebent said. "There is no fuel for fire in the vineyard because it's a very thick wood and it's green."

The fire destroyed much of Signorello's retail operations, including a commercial kitchen, tasting room, laboratories, offices and an apartment where the winery's owner, Ray Signorello Jr., and his family stay when they are in Napa. But remarkably, the blaze didn't touch the winery's most precious assets: a barrel cellar housing much of last year's wines, a tank farm where 2017 wines were aging – and the grapevines, some of which are almost 40 years old.

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"That's really kind of the fuel for our company," said Mr. Signorello, who was home in West Vancouver and was forced to watch the disaster unfold from afar. "Our wines are as good as they are because we've got beautiful old vines. I'm 54 and I can't wait another 38 years for the vines to get that age."

Mr. Birebent still has to test thousands of litres of cabernet sauvignon that were fermenting in stainless steel tanks close to the fire to look for signs of heat damage. But he believes the fire's effects on the region may prove to be far less than many wine enthusiasts may have feared.

"Everyone is going to start saying, 'Oh, it's going to be a bad vintage with smoke taint,' but it's not true," he said. "The wine is going to be beautiful, and Napa is still here and green and nice. It's not because we're missing a few wineries that the economy will change."

The future is less certain for the thousands of residents who were forced to flee their homes as flames swept through their neighbourhoods. Like much of California, Napa and Sonoma counties are facing a severe housing crisis that has pushed out many working- and middle-class families.

The fire levelled almost 5 per cent of the homes in Santa Rosa, the largest city in Sonoma County.

The blaze leaped over a freeway, tearing through Patrick Seawright's middle-class Coffey Park neighbourhood. He grabbed his two children, aged 5 and 12, and the family dog then fled.

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"We had to drive out and literally you couldn't see," he said. "The smoke was so thick. There was fire everywhere. Everything was burning."

The family spent the night at a church shelter before Mr. Seawright was able to return to the neighbourhood the next morning, where he found his home still standing.

Clint Rodda was not so lucky. For the past week, Mr. Rodda, his parents and his four-year-old son have been bouncing around between hotels and the homes of friends after the fire destroyed their house in Santa Rosa's upscale Fountaingrove neighbourhood.

His father found a rental in nearby Rincon Valley – until that neighbourhood, too, had to be evacuated.

"Where to go from here? That's a good question. I don't know where anyone is going to go," Mr. Rodda said while standing in line at a disaster relief centre.

Some residents are already talking about moving out of the area, he said, east to Sacramento or south to the San Francisco Bay area.

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He worries that his unstable living situation means he might have to leave his job as a sales manager for Red Bull in nearby Petaluma.

"People are going to have to restart their lives," he said. "But there's not going to be enough homes for thousands of families."

That thought weighs on Mr. Signorello's mind as he readies to rebuild his winery, a process he expects will take two years.

"That's another side of this that's tragic and difficult. A lot of people lost homes. Some people lost their lives," he said. "That won't go away quickly, those memories. But for the people that love Napa Valley and love our wine and love visiting, we'll be ready for them really soon."