It's Starting All Over!
It happens year after year. Although tourists can be seen in San Francisco all year round, the bulk of visitors really begin arriving in the spring and stay until early fall. By the summer, people from all over the world speaking different tongues can be heard everywhere.
Although domestic tourists, meaning Americans from out of town, do come year round, they mostly outnumber foreign arrivals right around Christmas time.
Whatever season it is though, San Francisco is a great and beautiful destination. Many say it is expensive. As a local, I say a stay in my adopted city need not be costly.