The overall average temperature for the month was 65 degrees. It was not the coldest August on record for downtown San Francisco, but it’s still significant. Not only was it colder than July, it was also colder than February — a month in which the temperature soared to 77 degrees one day.
“I got the perception that longer-time residents were fine with this ‘Fogust,’ especially since the last couple Augusts were warmer with less fog,” said Daniel Alrick, a meteorologist at the Bay Area Air Quality Management District. Alrick lives in San Francisco and runs a webcam from the Haight-Ashbury neighborhood, documenting the daily weather.
“I heard more complaints from newer residents, who were less accustomed to such a chilly summer,” Alrick added.
Why was it so cold in August? Why is there no such thing as summer there? The marine layer.
The temperature in San Francisco itself is highly controlled by its proximity to the cold Pacific Ocean. The air over the water, called the marine layer, is very cold and damp. Moisture easily condenses into tiny fog droplets. Since the temperature over land is often warmer than the air over water, a circulation sets up that pushes the fog inland, especially in the summer. The whole, damp air mass can waft over the entire city and drive temperatures down.
Fortunately for those newcomer residents, September is starting off warmer. San Francisco hit a toasty 82 degrees on Wednesday.