San Francisco is popular all year long. Summer is the high tourist season, so prices are higher, cues are longer and finding parking is never easy. San Francisco's summer weather is not very hospitable. The bay is often foggy, while inland or north in the Wine Country it's often hot and dusty and not very comfortable. Local weather is highly unpredictable; San Francisco usually has cool temperatures all year long due to its Mediterranean climate. The lowest average monthly low is 45.7°F in January, and the highest average monthly high is 68.5°F in September and October. Most rain falls from November to March. The month with the highest average rainfall is January, which averages 4.1 inches. During the summer months.