Last year’s drought had Napa Valley and Sonoma vineyards producing some of the best wines in a decade: Vines burrowed deeper in search of water to make a grape with more concentrated sugar and complex flavor. But most winegrowers don’t have a solid forecast about El Nino’s impact. “The winter’s rainfall total is only part of the story,” says David W. Graves, co-founder of Napa’s Saintsbury Winery, who adds that too cold (or too warm) temps can be bad for wine. Francis Ford Coppola Winery president Corey Beck adds: “For 2016 to be a great vintage, we need rain in California from December through February, until the growing season starts” — also known as the bud break, often in March — “then we want the rain to subside.”

But if El Nino doesn’t back off, says Beck, “botrytis [mold] will start forming on the vines and grapes, [which] can lead to a bitter finish on the palate.” Previous El Ninos, as in 1997-98, have resulted in great vintages, he says: “The 1997 vintage was a great year for all varietals. Cabernet sauvignon was a shining star in 1997. They had color, weight, depth and amazing intensity.” So, wine lovers, look to the skies: If it’s coming down through February, amazing cabs may be in store. But after March, your favorite vintages, not unlike your unproofed basements, may come dressed in mold.