Vineyard managers and growers in the Edna Valley area will keep a close eye on their grapes over the next few days to determine whether Thursday’s concentrated showers will harm their crops.

An unusual storm system passed over San Luis Obispo County on Wednesday and Thursday, stalling over a narrow area stretching from Pozo over San Luis Obispo to the Morro Bay-Los Osos area.

San Luis Obispo received more than half an inch of rain while areas north of Cayucos and south into Santa Barbara County received hardly any.

“It’s a little premature to see what kind of damage has been done,” George Donati, who manages vineyards in Edna Valley as general manager of Pacific Vineyard Co., said Friday.

Judging by past history, it will take three to five days before rot starts to develop in grape clusters, depending on how humid it is Friday and Saturday, he said.

“Hopefully (Saturday) when the sun comes out and the wind blows as predicted, it will help dry everything out, and we can get by with minimal damage,” Donati said.

Jean-Pierre Wolff, owner of Wolff Vineyards on the east side of the Edna Valley, said Friday’s cool and cloudy weather was not bad for his grapes.

“It allows the grapes to dry without having the heat that acts as a greenhouse,” he said.

While rain washed away any dust accumulation and reinvigorated the shallow roots, it may lower the sugar content of some of the grapes, particularly chardonnay, he said.

Wolff’s 125-acre property received about 0.80 inches of rain, making the ground a little muddy and possibly hazardous for workers on some of the steeper hillsides.

Wolff canceled harvest for two days and plans to resume next week. He’s already harvested the pinot noir and riesling grapes, as well as about a third of his chardonnay.

But he still has about 25 acres of chardonnay to harvest, as well as about 15 acres of red varietals, including syrah, petite sirah and teroldego.

Next week, Wolff hopes, “we will have some sunshine and can revert back to normal.”