Frost advisory has farmers scrambling for frost protection for vineyards

Below freezing temperatures that swept through Sonoma County on Wednesday had local grape growers turning on their fans and sprinklers to protect the tiny buds that have emerged on vineyards across the region.

The low Wednesday morning at Charles M. Schulz–Sonoma County Airport was 31 degrees and a frost advisory was scheduled from 2 a.m. to 9 a.m. Thursday for the North Bay as the temperatures were expected to drop to freezing, said Scott Rowe, a meteorologist with the National Weather Service. The high Wednesday was 55 degrees.

The spring freeze had vineyard managers protecting their crops as the buds on chardonnay vines have appeared, as well as some portion of pinot noir grapes, growers said. Bud break kicked off about a month ago, which signals the start of another grape-growing season.

Work crews for Bevill Vineyard Management turned on wind machines and sprinkler systems for vineyards located in areas of the Alexander Valley, Russian River Valley as well as the Dry Creek Valley, said owner Duff Bevill.

“They got to be on and running before it hits 32 degrees,” said Bevill. “Some ranches were colder than others.”

The wind machines mix warmer air above the vines with the colder air near to the ground to keep frost away, while sprinklers coat the vines in ice, which keeps the delicate bud at a constant 32 degrees and prevents damage.

Domenic Carinalli, a Sebastopol grape grower with about 100 vineyard acres, said he didn’t have to turn on his wind machines Wednesday morning but was preparing for the wakeup call early Thursday. When the temperatures reaches 34 degrees, Carinalli is notified by his phone and he can get up and turn on the five fans on his property. They will operate until about 8 a.m. when the sun has finally broken through, he added.

“It is pretty late this year,” Carinalli said of the frost advisory.

In recent years, frost has not presented the problems to local farmers as much as floods and the damage caused by wildfires. Carinalli noted he only had to turn his wind machine on twice in 2019 and once in 2018.

Typically, frost season in the county can last through May 15, though there have been freezing spells that have been later, and those can cause much damage as the buds start to bloom at that time. “You can get a killer frost around then,” Bevill said.

Fortunately for local farmers, the weather will get warmer heading into the weekend with highs in the low 60s and overnight lows in the 40s, Rowe said. Like Wednesday, some light rain should fall in the area on Saturday but then move swiftly through.

“We will have a few more drops in the bucket,” he said.

The rainfall total since Oct. 1 was 16.59 inches as of midnight Wednesday, which is only 53% of the historical average through the same time period.

A warming trend will emerge next week and by Monday highs should be in the 70s, Rowe said.

You can reach Staff Writer Bill Swindell at 707-521-5223 or bill.swindell@pressdemocrat.com. On Twitter @BillSwindell.