san francisco average temperature
Days of Hot Weather in San Francisco. San Francisco averages just two days a year when the temperature reaches 90 degrees Fahrenheit, and none over 100. No matter how warm the day, at night the temperature always cools to less than 70 degrees.The city's hottest days usually occur in September and October.an Francisco averages just two days a year when the temperature reaches 90 degrees Fahrenheit, and none over 100. No matter how warm the day, at night the temperature always cools to less than 70 degrees.