During the morning hours of January 11, 1951, a squall line pushed across the San Francisco Bay area. The storms produced millions of dollars in damage as straight-line winds and tornadoes ripped through the region. Per the Storm Prediction Center (SPC) and National Climatic Data Center (NCDC) databases, one twister occurred on this day, an F2 in Sunnyvale. Thomas Grazulis in Significant Tornadoes lists two tornadoes, the Sunnyvale F2, as well as an F2 at San Jose. Upon doing research, we were able to definitively confirm two additional tornadoes, one that moved through parts of Marin and Sonoma counties and a weak one in Contra Cosa County. It is likely that other funnels occurred, though reports in the newspapers were not detailed enough to confirm that.

Overview map showing the four confirmable tornadoes that occurred in the San Francisco Bay Area.

Two Rocks, CA


Path length: 17 miles

Width:  100 yards

Fatalities:  0

Injuries:  2

Rating:  F2

County:  Marin, Sonoma

Tornado Path

Corrected coordinates:  Start: 38.240774 / -122.978398   End:  38.323725 / -122.700478

Note:  Exact tornado path may not be straight and/or continuous.

Eyewitnesses watched a waterspout come ashore at Dillon Beach. Here, the funnel toppled many trees; one fell onto a home and crushed a garage and a new truck inside. It then skipped east-northeast through rural Marin County, where no damage was reported. The tornado may have dissipated and a new one formed at Two Rock in Sonoma County; since we cannot confirm this, we opted to list it as one twister.

At Two Rock, the funnel crested a hill and slashed a 100-yard wide swath across the Peter Christensen Ranch located on Bloomfield Road (now called Valley Ford Road), about 8 miles northwest of Petaluma, at 6:50 am PST. Mr. and Mrs. Jack Carson were asleep in the second story of their house. The home collapsed, and the couple awoke on the first floor with slight injuries. Trees surrounding their residence were stripped of all foliage and limbs, possibly even slightly debarked.

Mr. and Mrs. Christensen were also asleep in their newly built ranch-style house. Mrs. Christennsen was quoted in a January 12, 1951 copy of The Press Democrat as saying she “thought it was an atomic bomb. We didn’t know that ours was the only house struck in this neighborhood. It was awful.” The Christensen residence was still standing but had many broken windows and pieces of the roof blown off. 2×4’s peppered the exterior of the home. The tornado reportedly plucked a linen closet door from its hinges, carried it 15 feet down the hallway, through the bedroom, out the window, and it was not found. Elsewhere on the ranch, a 100-foot-long brooder house was swept away. Two garages, a barn, and a granary were also leveled.

The tornado whirled across the road and slammed into the Martin Iversen Farm. It missed the home but swept away 25 small chicken houses. They simply vanished, leaving only bare spots in the grass. It moved across Pepper and Mercham Roads, downing many trees and power lines.

Veering more toward the northeast, the funnel moved into Cotati. Numerous trees were twisted off in town about 3 to 4 feet above the ground. A large chicken house was leveled at the John Skelly Farm, killing one cow and 1500 chicks. This was the last damage reported before the vortex abruptly ended.

This tornado is not officially documented by the SPC/NCDC, nor is it listed in Significant Tornadoes. However, based on what happened at the Christensen Ranch, we estimate that it may have reached the F/EF2 range. 

Richmond-El Cerrito, CA


Path length: 3 miles

Width:  Unknown

Fatalities:  0

Injuries:  0

Rating:  F1

County: Contra Cosa

Tornado Path

Corrected coordinates:  Start: 37.891509/ -122.340253   End:  37.918326/ -122.295220

Note:  Exact tornado path may not be straight and/or continuous.

Glen Poshard, Manager of Anchor Bay Lumber, at Richmond Annex, watched as a waterspout formed over San Francisco Bay, and then moved onshore, hitting the lumber yard. Pieces of 4×4 planks were carried over a mile away. Extensive damage occurred to other buildings in the industrial area here. The writhing winds then followed a two-mile path, making its way to El Cerrito. It knocked down chimneys and signs. Multiple trees were toppled, and windows were blown out of buildings and cars. At one restaurant, the windows reportedly “exploded outward.” Approximately 50 houses sustained some form of damage. 

This tornado is not officially documented by the SPC or NCDC databases. We deduced that it was a twister due to eyewitness reports, as well as debris being carried over a mile. 

Sunnyvale, CA


Path length: 5.30 miles

Width:  880 yards

Fatalities:  0

Injuries:  30

Rating:  F2

County:  Santa Clara

Tornado Path

SPC coordinates:  Start: 37.37 / -122.12   End:  37.42 / -122.03

Corrected coordinates:  Start: 37.346475 / -122.087884   End:  37.390886 / -122.010594

Note:  Exact tornado path may not be straight and/or continuous.

At 8:17 am PST, the most destructive tornado of the outbreak, and one of the most intense in California history, hit Sunnyvale. It began in the Los Gatos residential area and moved northeast, destroying the Southern Pacific Railroad Station at the edge of Sunnyvale. A 32-ton crane was lifted from its track and thrown into the parking lot.

It then plowed through town, carving a half-mile wide swath. At least 150 homes were damaged, and 24 others were unroofed or moved from their foundations. Flimsy houses and buildings collapsed. Carrie Billalba lived on South Matilda Street. She was quoted in the January 12, 1951 edition of the San Francisco Examiner, “the wind suddenly ripped the door out of my hand. There was a noise like an explosion. People were in the streets screaming. I ran outside. Suddenly I saw the roof of our house sailing over another house. The air was filled with debris of every conceivable kind-roofs, fences, everything. I saw several houses off their foundations, and small garages just flattened.” At an eight-unit cottage court on El Camino Real, the roofs and frames of the buildings were crumpled. 

The Security Truck Line depot was unroofed. At the Westinghouse Electric Company plant, a 400×200 foot section of the roof was carried away. Part of the turbine machine shop was leveled. Thirteen people at the plant were injured. At the Woolridge Manufacture Company, a 10-ton crane was lifted and dropped 100 feet away. The glass fronts of several businesses including the new Red Rooster supermarket were smashed. 


We gathered information for this event from the SPC & NCDC Databases, the January 1951 Climatological National Data Summary (CDNS), newspapers.com and Thomas Grazulis in Significant Tornadoes and found the following differences:

Path Length:

  • The SPC/NCDC have a path length of 5.7 miles.
  • CDNS list a path length of 3-4 miles.
  • Grazulis lists a path length of 3 miles.
  • When you plot the damage, you get a 5.3 mile path.

    Path Width:

    • The SPC/NCDC do not have a path width documented.
    • CDNS has a 1000 yard path width.
    • Grazulis lists a 200 yard path width.
    • Multiple newspapers reported a ½ mile path (880 yards).


      • The SPC/NCDC/CDNS list 0 injuries.
      • Grazulis lists 30 injuries.

        San Jose, CA


        Path length: 2 miles

        Width:  100 yards

        Fatalities:  0

        Injuries:  1

        Rating:  F2

        County:  Santa Clara

        Tornado Path

        Corrected coordinates:  Start: 37.325177/ -121.902438   End:  37.343254/ -121.875159

        Note:  Exact tornado path may not be straight and/or continuous.

        At 8:45 am PST, the last confirmable tornado of the outbreak struck downtown San Jose. This twister is not documented by the SPC or the NCDC; however, it is listed by Thomas Grazulis in Significant Tornadoes. Per a January 12, 1951 article in the Oakland Tribune, Peggy Larson was sleeping in her mother’s home when she heard a “ripping sound.” The twister whisked away the roof and one of the exterior walls. Twenty-five other homes were unroofed. The funnel just missed city hall and damaged the tops of nearly 100 other buildings in downtown, and blew out thousands of windows. Many trees were toppled, and several cars were “spun like toys.” A warehouse collapsed. One person was injured when he was struck by a flying plank. 

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