Across the country, triple-digit temperature records were set in 150 places last year as the continental United States posted its warmest year on record, the government reported.
Sonoma County, bathed as usual in cool breezes off the Pacific Ocean, enjoyed mild weather, just right for growing a bumper crop of wine grapes.
"A perfect season," said Nick Frey, president of the Sonoma County Winegrape Commission.
Nearly 100 million people — about one-third of the nation's population — experienced 10 or more days of 100-degree or higher temperatures in 2012, the National Climatic Data Center said.
Santa Rosa's 170,000 residents sweltered at more than 100 degrees just twice — on Oct. 1 and 2.
At 100 degrees, people perspire and grapevines shut down, desiccating the fruit, Frey said.
Vines thrive at 87 degrees, he said, ideal for photosynthesis and for boosting the grapes' sugar level.
Growers had no complaints, bringing in a harvest of about 220,000 tons, or 10 percent above average. "It was nice," Frey said, adding: "It seldom is that way."
California joined the other 47 contiguous states in registering above-average temperatures last year, contributing to a 55.3-degree national average that was 1 degree warmer than the previous record in 1998 and 3.2 degrees above the average for the 20th century, the climate data center said.
Nineteen states had a record warm year and 26 more states has one of their 10 warmest. California's temperature tied for third highest on record.