"April was a cruel month for California winemakers, bringing a series of unusually late frosts to vineyards"

The Associated Press: Late cold snap puts a chill on California vineyards

The frosts hit all over Northern California, including Mendocino and Lake counties in Northern California as well as the Napa Valley and Sonoma County regions. The cold also was felt in Central Coast vineyards.

Damage was spotty, a hallmark of frost, with some vineyards mangled in only in a few corners.

Sinking temperatures dragged growers out of bed as frost alarms on vineyard thermometers went off.

Although a little frost isn't unusual, the cold snap that lasted 20 or more nights in some places was a first for many vintners.

"The last one we had that was anywhere near this brutal was back in the '70s," said Napa County Agriculture Commissioner Dave Whitmer.
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Another unknown is what the frost may have done to next year's crop — since vines are perennial, the area on the vine where buds for the 2009 harvest would form may have been damaged.