ADVICE: Dress in layers and bring a light jacket.

September is usually one of the nicest months weather-wise in San Francisco. The average high is 70 degrees, and the average low is 56 degrees. Contrary to popular belief, it is seldom "hot" in San Francisco; temperatures reach or exceed 80 degrees an average of only 21 days a year. Fog is a regular (and infamous!) feature of San Francisco summers. Even on the warmest days, the fog may roll in mid-afternoon, decreasing the temperature 10-15 degrees in just minutes. Mark Twain reportedly said, "The coldest winter I ever spent was a summer in San Francisco."

CONCLUSION: Be prepared for just about anything! Check the forecast before you come. Google "Weather 94104" for the most accurate information for downtown San Francisco.