The weather in Santa Rosa is one of the city's great drawcards. Sunshine lovers will be in seventh heaven with an average of more than 255 sunny days a year. The winter months are cool, though not especially chilly, and they do bring a fair amount of rain.
Summer, from June to August, sees average highs of 83°F (28°C). During winter, from December to February, the average high drops to 60°F (16°C).
As in nearby San Francisco, morning fog is fairly frequent in warm months, though it usually clears as the day goes on. Sometimes it rolls in again in the evening, so it's always a good idea to keep an extra layer or two to hand.
It's worth mentioning that Santa Rosa's location within California puts it at risk of wildfires. The city has been both threatened and directly impacted by several major wildfires in the past. It's vital to keep up to date on local conditions and heed all warnings and instructions from authorities.