Rare September Storm Brings SF Blustery Weather But Only Light Rain

The much-discussed early-season rainstorm arrived in San Francisco Sunday morning, bringing blustery weather and light showers but a bit less rainfall than initial forecasts had predicted.

Flooding and other rain-related hazards beyond slick roads are unlikely to impact San Francisco, Lisa Argen ABC7 Meteorologist, said in an interview.

As of late morning, light rain brought puddles to city sidewalks as precipitation accumulated to 0.11 inches, according to the observed precipitation map published by the National Oceanic and Atmospheric Administration (NOAA). 

While September rainfall isn’t unheard of, the month averages just a tenth of an inch of precipitation in SF. So today’s morning drizzles already single-handedly pushed the city into the rainy side of normal for all of September. And there’s more rain on the horizon. 

The latest forecast for SF’s downtown predicts that between a tenth and quarter of an inch could fall today. A thunderstorm is possible and expect a steady south wind that could gust as high as 37 mph. Heavier rainfall may arrive tonight, potentially accumulating as much as half an inch, according to the National Weather Service.

Trouble Further North

The region north of the city was much wetter Sunday morning. Over four tenths of an inch of rain had dropped on Kentfield, in Marin County, by 11 a.m., while Venado, in Sonoma County, logged 1.29 inches. The East Bay stayed relatively dry by comparison, with Oakland logging less than a tenth of an inch.

Tendrils of the same storm, the remains of Typhoon Merbok, wreaked havoc in Alaska on Saturday, causing widespread flooding that lifted some homes off their foundations and prompting evacuations.

This unseasonable storm isn’t going to be anywhere near enough to make much of a dent in a three-year drought, Argen said. And it’s unlikely to break any records. On this date in 1959, a whopping 2.01 inches of rain drenched San Francisco. The wettest September on record was 1904, when San Franciscans sloshed through 5.07 inches of precipitation, according to the National Weather Service.

Keep an eye out for rain delays if you’ve got tickets to see the Giants play at Oracle Park this afternoon and bring your poncho if you’re watching the 49er’s take on the Seahawks at Levi’s Stadium. Or find a dry hideout using one of The Standard’s guides to the city's great sports bars, bookstores or movie theaters. 

Damp conditions may continue through the beginning of the work week, but it’ll be safe to put away your umbrella once we reach Thursday. Don’t stick it too far in the back of the closet; SF’s rainy season typically begins in October.