There's calendar winter, and then there's San Francisco winter. Sometimes they collide (Dec/Jan/Feb) but usually it goes down like this, and have bolder when the San Francisco winters typically show up:

• August - warm
• September - very warm to hot
• October - very warm until Halloween, then excruciatingly cold just in time for the Halloween party
• November - somehow sort of warms up again, but on the cool side. Maybe a touch of rain.
• December - cool, temperate. Some rain. Evenings get pretty chilly, but the sun holds on during the day
• January - mix of warm and cold days. Can't really tell what's going on. Some rain.
• February - the fleece jacket comes out as a daily later. Daytime can still get warm.
• March - winter is here! Night clocks below freezing a few times.
• April - some rain. Cool.
• May - winter is over! Yay!
• June - winter is back! Evenings can be quite cold. Your fleece comes back out into the rotation
• July - warm and cool until the end of the month. Then it the hot streak can start in multiple day incremental