A storm system moved into Sonoma County overnight bringing some rare June rain and slowing the morning commute in some places.

The wet weather blew in from the Pacific Sunday night and is expected to last until Wednesday morning, according to the National Weather Service. Sonoma County should see 1-2 inches of rain over the next two days, which could cause problems for drivers but should not affect grape growers.

"It's unusual to get measurable amounts of rain this time of year," said Bob Benjamin, a meteorologist with the National Weather Service. "The slick roadways are going to be the main concern."

Traffic was slow through Petaluma on Monday morning, though CHP did not report any accidents on Sonoma County highways as of 7:30 a.m.

The rain will be little more than a nuisance for most grape growers, who may lose a day or two in the fields, said Karissa Kruse, president of Sonoma County Winegrowers.

The vines are past their delicate blooming stage when rain can interfere with self-pollination, Kruse said. And the green fruits don't yet contain sugar, so mildew is not yet a concern, she said.

"If there's a good time for (unseasonable rain), right now it's going to have the least effect," Kruse said.

Wednesday should bring sunny weather with temperatures into the 80s, Benjamin said. The warm weather should last into the weekend.

You can reach Staff Writer Matt Brown at 521-5206 or matt.brown@pressdemocrat.com