Alameda County, California: Natural Disaster Risk and History
Alameda County, California has a Very High natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 99.8 out of 100, higher than about 99% of US counties, with earthquakes, landslides and inland (river and flash) flooding scoring highest of its 18 hazards and $1.9 billion a year in expected losses.
OpenFEMA lists 22 federal disaster declarations that included Alameda County since 1970, not counting 2 for COVID-19; the latest is DR-4699-CA (Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides, declared 3 April 2023). NOAA's Storm Prediction Center recorded 3 tornadoes touching Alameda County from 1950 to 2025.
Live weather alerts for California All official warnings Latest FEMA declarations
Population 1,678,284 Buildings worth $373 billion Area 830 sq mi Risk rank in California 3 of 58 FIPS 06001
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Earthquake | Very High | 100.0 | $1.4 billion | about once every 7.2 years | — |
| Landslide | Relatively High | 99.8 | $5.7 million | about 25 a year | — |
| Inland flooding | Very High | 99.7 | $491 million | about 2.3 a year | 63 |
| Wildfire | Relatively High | 97.7 | $12 million | about once every 173 years | — |
| Heat wave | Relatively High | 97.6 | $13 million | about 7.1 a year | 85 |
| Coastal flooding | Relatively High | 86.0 | $4.6 million | about once a year | — |
| Drought | Relatively Moderate | 85.9 | $1.4 million | about 58 a year | 2,338 |
| Volcanic activity | Very Low | 78.8 | $348 | rarer than once in 1,000 years | 2 |
| Tornado | Relatively Moderate | 65.8 | $2.4 million | about once every 11 years | 2 |
| Tsunami | Relatively Low | 60.0 | $3.1 million | about once every 2.9 years | 73 |
| Lightning | Relatively Low | 47.5 | $234,668 | about 4.5 a year | 84,760 strikes |
| Hail | Relatively Low | 35.8 | $166,803 | about once every 25 years | 1.6 |
| Strong wind | Very Low | 11.3 | $93,955 | about once every 25 years | 2 |
| Avalanche | Very Low | 6.6 | $4 | about once every 100 years | 0 |
| Winter weather | Very Low | 4.3 | $3,285 | about once every 1.4 years | 12 |
| Cold wave | No Rating | 0.0 | — | — | 0 |
| Hurricane | Not Applicable | — | — | — | — |
| Ice storm | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 22
Most common: Severe Storm 8, Flood 7, Fire 2, Hurricane 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1970s | 3 | Drought, Fire, Flood |
| 1980s | 4 | Flood ×2, Earthquake, Coastal Storm |
| 1990s | 6 | Severe Storm ×4, Fire, Freezing |
| 2000s | 3 | Severe Storm ×2, Hurricane |
| 2010s | 3 | Flood ×2, Severe Storm |
| 2020s | 3 | Flood ×2, Severe Storm |
The last 10
Widest declarations that included Alameda County
- Hurricane Katrina Evacuation (2005, EM-3248-CA): 58 California counties designated.
- Severe Winter Storms, Flooding Landslides, Mud Flow (1995, DR-1046-CA): 57 California counties designated.
- Severe Storms, Flooding, Mud and Landslides (1997, DR-1155-CA): 48 California counties designated.
Named storms in its declarations: Hurricane Katrina (2005).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. California also had 30 statewide declarations with no county list.
Tornado record since 1950 3
| Tornadoes touching the county | 3 |
|---|---|
| Strongest-rated | (E)F0 ×3 |
| Peak month | March (1) |
| Deadliest | — |
| Longest path | 25 Apr 1994, F0, 0.7 mi path |
| Most recent | 25 Apr 1994, F0, 0.7 mi path |
| Deaths / injuries on those paths | 0 / 0 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 3 | 0 | 0 | 0 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 0 | 0 | 0 | 1 | 2 | 0 | 0 | 0 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How Alameda County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Alameda County (this page) | — | Very High | 99.8 | Earthquake |
| Contra Costa County | 30 km | Very High | 99.5 | Earthquake |
| San Mateo County | 46 km | Relatively High | 99.2 | Earthquake |
| Santa Clara County | 49 km | Very High | 99.7 | Earthquake |
| San Francisco County | 50 km | Very High | 99.5 | Earthquake |
| San Joaquin County | 63 km | Relatively High | 98.6 | Drought |
Nearest by distance between county centres. Every county in California, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Low 27.5 |
|---|---|
| Community resilience | Very High 91.2 |
| Community risk factor | 0.94 |
| Expected annual loss, all hazards | $1.9 billion |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for Alameda County's main hazards
- Right now: National Weather Service alerts for California · all official warnings on Global Incident Tracker.
- Earthquake: Earthquakes today · Earthquake safety guide
- Landslide: Landslides recorded
- Inland flooding: Flood safety: why shallow water kills · Floods recorded
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about Alameda County
What natural disasters is Alameda County, California most at risk from?
Alameda County, California has a Very High natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 99.8 out of 100, higher than about 99% of US counties, with earthquakes, landslides and inland (river and flash) flooding scoring highest of its 18 hazards and $1.9 billion a year in expected losses.
How many federal disaster declarations has Alameda County had?
OpenFEMA lists 22 federal disaster declarations that included Alameda County since 1970, not counting 2 for COVID-19; the latest is DR-4699-CA (Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides, declared 3 April 2023). Another 30 California declarations were made statewide without a county list.
How many tornadoes have hit Alameda County?
NOAA's Storm Prediction Center recorded 3 tornadoes touching Alameda County from 1950 to 2025.
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.