San Francisco Weather in the summertime is cool. The average starting temperature is: 56 degrees Fahrenheit. The temperature at the finish line ranges from 64 – 70 degrees Fahrenheit.
San Francisco is a city with microclimates and submicroclimates. Due to the city’s varied topography and influence from the prevailing summer marine layer, weather conditions can vary by as much as 9°F (5°C) from block to block. Each neighborhood is known to have varying weather patterns. Since The SF Marathon runs through dozens of neighborhoods, you’ll want to wear layers. It is typical for Race Day to be cool and foggy in the early miles, and warm up with clearer skies in the later miles. Temperatures may change by about 10-20 degrees Fahrenheit during the run.