Some vineyards prune as early as November; others as late as early March. Generally, March is a time for vineyard maintenance, vacations, bottling, winery cleaning – at Ramey Cellars (where I was a cellarrat for the 1st half of 2011) many of the 2010 wines in barrel were completing Malolactic Fermentation.
I also have notes that it was sunny and warm at the end of March. 22C – 30C (70-86 degrees F) around the Russian River, Alexander Valley and Dry Creek. In Oregon there was plenty of driving rain and snowstorms in the Siskiyou Mountains when I went to visit Mom and wineries in The Willamette Valley. They are 3 weeks behind “normal” for the 2011 vintage.