Cold, wet weather is on the way early next week, when a series of winter-like storms are expected to bring rain to the North Coast and snow to the Sierra, the National Weather Service warned Thursday.
The change is expected to be so significant that the weather service has issued a "special weather" alert for most of Northern California, in part so anyone traveling to the high country can be forewarned about winter conditions, National Weather Service meteorologist Steve Anderson said.
In Sonoma County "it will be on the order of 30 degrees cooler than (Wednesday) by the middle of next week," Anderson said Thursday.
An onshore sea breeze cooled down the region Thursday, when temperatures peaked in Santa Rosa at 75 degrees — already a significant drop from a high of 97 one day earlier.
Temperatures were forecast to fall another 10 degrees or so through the weekend before the rain arrives Monday or early Tuesday.
Forecasters expect a quarter- to a half-inch of rain north of the Golden Gate Bridge on Monday as the first front passes through the area.
Another, likely stronger wave of cold, wet weather with high winds and heavy rain was expected to come through the region Wednesday into Thursday, Anderson said.
"It's a winter-like storm, early — about three weeks early," Anderson said. "Typically we see our first one toward the end of October."
The looming storm is an added stress for winemakers around Sonoma County, where harvest got off to a late start because of the cool summer.
Only 20 percent of the county's $400 million grape crop will be harvested by the end of this week, leaving the vast majority of the crop exposed, estimates Nick Frey, president of the Sonoma County Winegrape Commission.