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SouthsanfranciscoPhoto: Coolcaesar at English Wikipedia · CC BY-SA 3.0
D−Hazard risk
Natural hazards in South San Francisco · FEMA

FEMA expects more hazard damage per building in South San Francisco than in 96% of U.S. towns, mostly from earthquakes

On FEMA’s National Risk Index, South San Francisco gets a D− for hazard risk: higher expected damage per building than 96% of U.S. towns, #648 of 847 in California. Most of that expected damage is earthquakes (67%), then river and rain flooding (32%). Flood insurance has paid 76 claims here since 1982.

Earthquakes 67%River and rain flooding 32%

Graded on FEMA’s expected yearly building damage per dollar of building value (NRI v1.20, December 2025), weighted by where residents live; flood claims are shown, not graded. How hazard risk is graded

more than 96%of U.S. townsLess damageMoreExpected yearly damage per dollar of building, vs. the 21,298 U.S. towns we grade#648 of 847 in California
Hazard risk
D−#648 of 847
in California · higher than 96% of U.S. towns
Main hazard
Earthquakes
67% of expected building damage
Flood claims
76
paid since 1982 · $3.7M
Flooded more than once
11
properties · 1 “severe repetitive loss”
Disasters paid out here
4
of 19 declared for San Mateo County

What stands out about South San Francisco’s natural hazards

From FEMA’s model and FEMA’s records, below.

FEMA-funded flood-proofing1 building floodproofed with FEMA grants.Remembers 201422 flood claims were paid for 2014 alone, the most of any year.
By hazard

What South San Francisco faces

Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.

Earthquakes

67%of expected building damage
Well above average · in the top 1% of U.S. census tracts

River and rain flooding

32%of expected building damage
Well above average · higher than 87% of U.S. census tracts
Recorded about once a year in the area
Smaller shares here
 Coastal flooding Tornadoes Hail Strong wind Wildfire Winter storms Heat waves Landslides Lightning Tsunamis top 1%
FEMA models no building damage here
HurricanesIce stormsCold wavesAvalanchesVolcanic activity

Shares are of FEMA’s expected building damage, the measure the grade uses; ranks compare each hazard’s building-damage rate with all 85,154 U.S. census tracts. In FEMA’s terms, river and rain flooding is FEMA’s “Inland Flooding” (rivers and streams overflowing their banks, or rain overwhelming drainage). FEMA defines coastal flooding as high or rising tides and storm surge, so surge damage is counted there. Drought isn’t listed: FEMA counts its losses in crops only.

Flood risk changes street by street. Check a specific address on FEMA’s flood map, and ask about flood insurance before you buy.
Hazard risk grade

What’s behind South San Francisco’s grade

Earthquakes are 67% of the building damage FEMA expects in South San Francisco, and South San Francisco’s rate of earthquakes damage is in the top 1% of U.S. census tracts. Next is river and rain flooding at 32% (higher than 87% of U.S. census tracts).

Where South San Francisco sits
South San Francisco
Least damageMiddleMost damage

D− #648 of 847 in California; higher expected damage per building than 96% of U.S. towns (21,298).

South San Francisco’s residents live in 15 census tracts; FEMA’s figures are combined by where they live.

What drives the damage to buildings
Earthquakes67%River and rain flooding32%Everything else1%

The typical California town has higher expected damage than 92% of U.S. towns; within the state, South San Francisco has more expected damage per building than 76% of California towns.

In dollars, FEMA expects about $89.1M a year in losses across South San Francisco: $67.0M to buildings, the rest to people and crops.

A firm figure. It combines 15 census tracts by where South San Francisco’s residents live. FEMA’s model is an average year for today’s buildings, not a record: the claims and disasters below are the record.

How TownRatings grades hazard risk →

Flood insurance claims

Does South San Francisco flood? Sometimes: 76 flood claims since 1982

Every paid claim on a federal flood insurance policy in South San Francisco, from FEMA’s records: 3.2 per 1,000 homes, fewer than 50% of the 13,809 U.S. towns with a flood insurance record.

Paid flood claims, by year
1982: 7 claims1983: 4 claims1984: 0 claims1985: 0 claims1986: 0 claims1987: 0 claims1988: 0 claims1989: 2 claims1990: 0 claims1991: 0 claims1992: 0 claims1993: 0 claims1994: 0 claims1995: 0 claims1996: 1 claim1997: 0 claims1998: 4 claims1999: 0 claims2000: 1 claim2001: 0 claims2002: 10 claims2003: 1 claim2004: 6 claims2005: 3 claims2006: 1 claim2007: 0 claims2008: 0 claims2009: 0 claims2010: 0 claims2011: 0 claims2012: 0 claims2013: 0 claims2014: 22 claims2015: 1 claim2016: 7 claims2017: 0 claims2018: 0 claims2019: 0 claims2020: 0 claims2021: 4 claims2022: 1 claim2023: 1 claim2024: 0 claims2025: 0 claims2026: 0 claims198220022014
19822026
Biggest named events
  • The Pineapple Express - Southern3 claims · $18K
  • The California Atmospheric River2 claims · $56K
76
paid claims since 1982
$3.7M
paid to owners
11
homes flooded more than once
$48K
average claim
Homes that flooded again and again
FEMA “severe repetitive loss” (1)Flooded 2+ times
of homes in flood zones are insured
of all homes are insured
No community discount

South San Francisco isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.

Insurance rates: San Mateo County.
What’s been done with FEMA grants
1building floodproofed
Disasters

4 federal disasters brought FEMA money to South San Francisco

Disasters that paid out in South San Francisco itself (aid to households or repair grants to the City of South San Francisco), newest first, with that year’s flood claims.

  1. 2022Severe Winter Storms, Flooding, Landslides, and Mudslides67 households applied for aid$165K aid approved$492K to the City of South San Francisco for repairs1 flood claim paid that year
  2. 2020Wildfires37 households applied for aid$1K aid approved
  3. 2006Severe Storms, Flooding, Landslides, and Mudslides$2K to the City of South San Francisco for repairs1 flood claim paid that year
  4. 2005Severe Storms, Flooding, Mudslides, and Landslides$86K to the City of South San Francisco for repairs3 flood claims paid that year
Disasters declared, by decade
Paid out in South San FranciscoSan Mateo County only

San Mateo County has had 19 natural disasters declared by the President since 1953, most often severe storms, then floods. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.

Also 2 FEMA wildfire suppression grants (Fire Management Assistance, not a disaster declaration) for fires in San Mateo County, 2010–2020.

Were you here?

Old photos of South San Francisco after a storm or flood belong in the town’s history. Add one, or share what you remember below.

Add to the South San Francisco archive →
Next door

South San Francisco and its neighbors

South San Francisco is 6th of the 7 graded towns here, from least expected damage per building to most. Tap a town to see its hazards.

San Bruno: hazard risk DDaly City: hazard risk DColma: hazard risk DPacifica: hazard risk DBrisbane: hazard risk DOakland: hazard risk D−San BrunoDaly CityColmaPacificaBrisbaneOaklandSouth San Francisco
Lowest fifthSecondMiddleFourthHighest fifth
TownHazard riskMostly (buildings)Flood claims
BrisbaneDmore damage than 90%earthquakes3
Daly CityDmore damage than 92%earthquakes23
PacificaDmore damage than 94%earthquakes76
San BrunoDmore damage than 94%earthquakes22
ColmaDmore damage than 94%earthquakes1
South San FranciscoD−more damage than 96%earthquakes76
OaklandD−more damage than 97%earthquakes103

Hazard risk = FEMA’s expected yearly building damage per dollar of building value, vs. the 21,298 U.S. towns we grade; the map is shaded by fifths of the same scale. Flood claims = paid federal flood insurance claims on record.

Be ready

Get ready for what South San Francisco faces

A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.

Earthquakes
  • Drop, cover and hold on.
  • Strap tall furniture and the water heater to the wall.
  • Know how to shut off the gas.
More from Ready.gov ↗
When the river rises
  • Turn around at flooded roads: a foot of moving water can carry off a car.
  • Flood insurance usually takes 30 days to start, so buy it before the forecast.
  • Keep papers and medicines up high, in a grab-and-go bag.
More from Ready.gov ↗
Before you buy or rent
  • Look up the address on FEMA’s flood map.
  • Ask the seller or landlord whether it has ever flooded, and what flood insurance costs there.
  • Get a flood insurance quote early: policies usually start 30 days after you buy.
When a storm is coming
Forecast and alertsWeather →911, the nearest ERSafety →

Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.

Questions about natural hazards in South San Francisco

Is South San Francisco at risk for natural disasters?

On FEMA’s National Risk Index, South San Francisco has higher expected damage per building than 96% of U.S. towns: D− for hazard risk, #648 of 847 in California. Most of the expected damage is earthquakes (67%) and river and rain flooding (32%). This is FEMA’s model of an average year for today’s buildings, not a forecast.

Does South San Francisco flood?

Flood insurance has paid 76 claims in South San Francisco since 1982, $3.7M in all, or 3.2 per 1,000 homes, fewer than 50% of U.S. towns with a flood insurance record. 11 properties have flooded more than once. The most claims came from Pineapple Express - Southern (3).

Is South San Francisco in a flood zone?

Flood zones are drawn street by street, so the answer depends on the address: look it up on FEMA’s flood map. In San Mateo County, 31% of homes in mapped flood zones carry federal flood insurance, and 1.8% of all homes do.

How much is flood insurance in South San Francisco?

FEMA’s Community Rating System list shows no discount for South San Francisco’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.

What was the biggest storm in South San Francisco?

By FEMA money that reached South San Francisco, Severe Winter Storms, Flooding, Landslides, and Mudslides (2022): 67 households applied for aid, $165K approved, and $492K to the City of South San Francisco for repairs. By flood claims, Pineapple Express - Southern: 3 paid, $18K.

Is South San Francisco at risk from earthquakes?

It is the largest share of the building damage FEMA expects here (67%), and South San Francisco’s rate for it is in the top 1% of U.S. census tracts.

Storm stories

Memories, warnings and help from neighbors in South San Francisco.

Town Square →
Start the conversation

Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where South San Francisco’s residents lived in the 2020 census; OpenFEMA: NFIP redacted claims, multiple-loss properties, community status book and residential penetration rates, housing assistance (owners and renters), public assistance funded projects, hazard mitigation properties and disaster declarations. Homes: Census ACS 2020–24. Preparedness tips: Ready.gov. FEMA’s model is an average of expected damage, not a forecast. How hazard risk is graded.