Wine growers on the Sonoma Coast and in the Russian River Valley face a nail-biting wait to discover if 2010 will be a great vintage – or ruined by rain.A low pressure system sitting off California's north coast has created highly unusual weather conditions in the area this summer, with coastal fogs and temperatures in the 60s and 70s Fahrenheit, rather than the more normal 80s and 90s. As a result, grapes have ripened slowly, giving the potential for exceptional quality – but growers are concerned that they might not be able to finish the harvest before the onset of October rain.