California North Coast wine grape season off to wild-weather start amid frost, water concerns

This year’s North Coast wine grape crop got off to an encouraging start, but unusual weather swings at a critical time in vine development, the prospects of a third year of drought and lingering uncertainty about wine demand are causes for concern among some market watchers.

Some of the warmer areas of the region, namely Sonoma County’s Alexander and Dry Creek valleys, are seeing the beginning of bloom, when vines self-pollinate, resulting in grape clusters, according to brokers.

That time of vine self-pollination to form grape clusters had reached less than 10% of the region as of May 10, according to Christian Clear, who oversees North Coast grape deal-making for Novato-based Turrentine Brokerage. Vines didn’t appear near bloom in Napa Valley, and those in Lake and Mendocino counties were behind that.

This is a time of the season when growers want Goldilocks weather — not too hot, cold, cloudy or windy. That’s because disruptions in a vine’s prepping itself for grape cluster formation, a process called “set,” can result in undeveloped berries in clusters, a feared outcome called “shatter.”

At stake is the $1 billion-plus annual crop from the premium grape-growing region, which encompasses Napa, Sonoma, Mendocino, Lake and western Solano counties. The region’s crop size last year of 400,000 tons was down 13% from the five-year average, a drop attributed to drought, but last year’s harvest was up from 2020, which came in 29% below average because of the wildfires that year.

“It’s shaping up to be a good potential crop, minus the hit-and-miss frost we’ve been receiving,” Clear said.

After heavy rains at the end of last year, the region experienced weeks of dry, sunny days, and that coaxed vines to push out buds in February, an early awakening from the typical winter nap. But then came bouts with frost in late February, early April, a heavy rain storm later that month followed by a few days of frost in the first half of this month.

Pockets of the North Coast have suffered from frost, according to Clear and Glenn Proctor, a partner with San Rafael-based wine and grape brokerage Ciatti Co. Areas with reports of potential frost damage include Pope and Childs valleys in eastern Napa County, the Carneros region straddling southern Napa and Sonoma counties, parts of Lake and Mendocino counties, and corners of Sonoma County vineyards where frost-protection sprinklers didn’t reach.

Some couldn’t get their frost-protection wind machines or sprinklers turned on fast enough as temperatures plummeted. Others have been having to weigh frost protection or water conservation.

“In Mendocino County, people are having to make some pretty tough choices on saving their water through the growing season or using it to protect the vines right now,” Clear said. “And from what I can tell, people are using it right now to protect the vines and hoping that the state doesn't curtail too much of their water resources out of the Russian River and Lake Mendocino.”

State water regulators are poised to cut earlier this year than last year how much water can be diverted this summer from waterways in the Russian River watershed in Mendocino and Sonoma counties.

Despite the spotty frost issues and colder weather overall this spring, which are fingered for delayed vine flowering in the region, the North Coast is in better shape than other key winegrowing regions in the state that were hard hit by frost, particularly the Lodi area, Proctor said. Those areas also are facing further cutbacks in water allocations from state systems.

“It hasn’t been easy year with water,” Proctor said. “We were hoping to have this be a normal year, but (weather has) been a little erratic. But we think we’ll come out of this fine. Certain growers will be affected more than other growers.”

Jeff Quackenbush covers wine, construction and real estate. Before coming to the Business Journal in 1999, he wrote for Bay City News Service in San Francisco. Reach him at or 707-521-4256.

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