Working with vintners, growers and weather stations around Napa Valley, the Scripps science team collected data from 12,000 points in Napa Valley and from this massive collection of grass-roots data, assembled its final report: "Climate and Phenology in Napa Valley: A Compilation and Analysis of Historical Data" by Dan Cayan, Kimberly Nicholas, Mary Tyree and Michael Dettinger.
The report, released in February 2011, indicates that Napa Valley has warmed slightly over recent decades, but not to the degree that has been reported in the studies noted above, which analyze broader California weather station data. According to the Napa Valley-specific data analyzed for our report, the warming we have experienced, one to two degrees Fahrenheit, has taken place primarily in overnight temperatures between the months of January to August. In fact, Napa Valley has actually experienced cooler daytime temperatures and increased marine fog influence during the summer growing season in recent years.
Napa Valley Vintners