The most common question I get this time of year is, "Will the cold weather hurt the grapevines?". The simple answer is "nope, not even a little."
Vines go dormant like apple trees or roses during the cold winter months. The sap pushes back down into the roots to stay warm and the wood hardens off to protect the tender part of the plant. Vines will go happily through the winter as long as the temperature doesn't drop below -15F, something that just never happens in California.
There's no real threat of damage to the plant until it begins to have bud break again. That's the point when a lot cold snap or frost can damage the tender new shoots. When the vine looks like this there's danger from cold:
We're still at least a few weeks away though from the plants pushing open. We also have the added protection in each of our mountain vineyards of being on a good slope. Cold air is heavy and it moves down the slope, this helps prevent frost from forming, so we don't really have any cold worries at all.
The lack of rain is a bit more bothersome. Unless we make up for the loss of rain in the months ahead it means we'll have to think about turning on the drip systems in our vineyards this spring and summer, more than we might do otherwise. It's a small change, and just means we have to be even more attentive to how the plants are doing.