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Snow fell briefly late Friday and early Saturday on the city's Twin Peaks neighborhood and some other areas with higher elevations, meteorologist Mark Strobin said.
"A little bit up in the hills," Strobin told The Associated Press. "It snowed down to about 400 feet."
But there was only rain downtown and in other many other areas of the near sea level city, and the snow that did fall disappeared rapidly.
The city last saw snow on the ground in 1976, when an inch fell.
Strobin said the higher regions might have had other snow dustings since that measureable snow fell 35 years ago. He said it was still too early to tell how this event will be recorded in the books.
Strobin, who is based in Monterey, Calif., said that city also got a rare dusting of snow.
A storm system moving across Northern California responsible for the snow also dumped more than 2 feet of snow in the Sierra Nevada mountains.
Just the idea of possible snow had the tech-savvy city from looking skyward with anticipation.
One blogger posted a pretend ski map, noting possible beginner, intermediate and expert runs in the city's hilly Bernal Heights neighborhood. A newly created website — isitsnowinginsfyet.com — gives a simple answer for anyone who is wondering.
The San Francisco Chronicle posted old photos of snow from 1882, 1951, 1964 and other rare instances of city snowfall — including one photo from the 1976 storm that shows gleeful school kids throwing snowballs.
On Friday, the storm prompted San Francisco Mayor Ed Lee to take precautionary measures. He urged residents to watch out for icy road conditions, and, if possible, avoid driving during the storm's peak. The city's public works department was planning to offer free sandbags and emergency crews were on stand-by.
For snow to fall and accumulate in San Francisco, temperatures must drop to 36 degrees, precipitation must be falling and the ground must be chilled for several days beforehand, said Steve Anderson, also a National Weather Service forecaster.
Though it rarely gets that cold in San Francisco, where the surrounding bay and Pacific Ocean generally keeps temperatures moderate, temperatures in San Francisco were expected to drop into the 30s overnight, according to the National Weather Service.