Cold snap could trigger problems for North Bay grape growers

Plummeting temperatures this week are cause for concern among some North Bay grape growers, prompting fears that the unseasonably cold conditions could damage their crops.

The National Weather Service issued a freeze warning for much of the Bay Area between 2 a.m. on Wednesday and 9 a.m. on Friday. The warning covers almost the entirety of Sonoma County, excluding the coast.

Temperatures are expected to dip as low as the mid-20s overnight and daytime highs will be in the mid- to upper 50s — about 10 degrees below normal for late February, meteorologists said.

Weather officials warned that the cold conditions could damage or kill sensitive vegetation, cause problems for unprotected outdoor plumbing and be hazardous to people and animals.

Local homeless advocates said they were concerned that the cold spell could be dangerous for those living outside, and some were working to set up temporary shelters.

For local grape growers, concerns about the chilly conditions were exacerbated because a streak of unseasonably warm temperatures earlier this month contributed to an early bud break on vines in certain pockets around the region. Those young buds are now threatened by freezing weather unless farmers take protective action.

That either includes using wind machines to move warmer air above the vines, or using overhead sprinklers that can coat vines in ice, which can keep buds at a constant temperature of 32 degrees and prevent further damage.

“It’s going to be a nail biter,” said Brian Clements, a partner at Turrentine Brokerage, a Novato-based grape broker.

At Paradise Ridge Winery located in the hills of Fountaingrove, buds have broken on about 50% of the chardonnay vines, almost a month earlier than usual, said Rene Byck, co-owner of his family’s winery.

“That process started really early because of the warmer weather,” Byck said. The winery’s pinot noir and sauvignon blanc vines have been mostly dormant.

The winery has neither wind machines nor sprinklers, as frost has typically not been a problem for the business since it opened in 1994, Byck said. He recalled only one frost episode about 10 years ago that significantly lowered the winery’s yield.

“We got lucky in the past,” he said. “We are hoping that luck continues with the cold weather spurt.”

The areas likely to have the most trouble with the cold snap are ones where the growing season starts earliest, such as the Carneros region by San Pablo Bay, Clements said. Those low-lying areas have predominantly pinot noir and chardonnay vineyards.

Local growers have experienced two consecutive harvests with yields below the average over the past 10 years of 476,684 tons. The 2021 crop was at nearly 400,000 tons.

“If frost comes, it’s going to make a balanced market (now) short,” Clements said of the North Coast wine grape supply.

The warm weather ended Sunday, and as the region began to cool off, meteorologists were anticipating the arrival of rain.

The cold front coupled with the weather system moving through the region Tuesday afternoon brought hail to parts of the East and North Bay, including Sonoma and Napa.

“This is the time of year when we most expect this kind of thing — late winter into spring,” said Sean Miller, a meteorologist for the weather service in Monterey. The conditions “are bringing really cold air aloft” and then “dropping the hail” on the parched region.

As of Tuesday afternoon, Miller said, most of the North Bay areas that saw precipitation received a tenth of an inch and won’t receive much more by the time the system rolls through.

The frozen showers would likely come to an end Tuesday night, Miller said.

By Tuesday morning, Santa Rosa had seen only a light overnight sprinkle. A rain gauge at the Charles M. Schulz-Sonoma County Airport measured less than 0.01 inches of rain — not enough to be considered “measurable” precipitation, weather service meteorologist Sarah McCorkle said.

“So far it’s just a trace,” she said.

The last time there was measurable rain — at least 0.01 inches — at the airport was on Jan. 7, when the gauge logged 0.15 inches.

Since then, trace amounts of rain have been recorded six times: Jan. 12, 16, 20 and 26, Feb. 14 and Monday night.

The 45-day streak without measurable rain in Santa Rosa meant that the city on Monday was in its second-longest dry spell ever recorded during the rainy season between mid-October and mid-March, according to McCorkle.

The longest dry streak, 60 days, lasted from Oct. 9 to Dec. 7, 1929.

Elsewhere in the Bay Area, weather officials said the dry spell was broken by Monday night’s rain.

Downtown San Francisco, for example, got 0.04 inches of rain, ending its 44-day streak, according to the weather service.

The chilly conditions this week come after several days of unseasonably warm temperatures across the Bay Area. On Thursday, which was the hottest day of the streak, the high of 79 degrees at the airport tied the record for that date, which was previously set in 2020. The normal temperature for the day is 61 degrees, according to the weather service.

You can reach Staff Writer Matt Pera at matthew.pera@pressdemocrat.com. On Twitter @Matt__Pera.