San Francisco Climate & Weather Averages

Climate Insights from Our Writers

“San Francisco's climate is the most misunderstood of any city I've studied. The famous quote attributed to Mark Twain — 'The coldest winter I ever spent was a summer in San Francisco' — captures something essential about the city's weather patterns. The data shows that September is actually the warmest month, averaging 17°C, while January is the coolest at 11°C. The annual temperature range of just 6°C makes San Francisco one of the most thermally stable cities I've recorded, but the daily variation and the wind are the real factors that define the experience. The city's position on a peninsula between the Pacific Ocean and San Francisco Bay creates a complex system of wind and fog that can change dramatically within a few hours. The fog, which locals call 'Karl,' flows through the Golden Gate and can blanket the western neighborhoods while the eastern parts of the city remain sunny and warm. The best time for a visit is September through October, when the fog is less persistent, the temperatures are warmest, and the city's outdoor attractions — Golden Gate Park, the waterfront, the hills — are at their most accessible. The summer months of June through August are actually the foggiest, with the marine layer creating cool, overcast conditions that can persist throughout the day. The winter months are cool and wet, with most of the city's 600mm of annual rainfall falling between November and March. For travelers, the key to enjoying San Francisco is ignoring the calendar and focusing on the hour — the city's weather can change dramatically within a single day, and the best strategy is to dress in layers and be prepared for anything.”

— Climate & Travel Writer