San Joaquin County, California Natural Disaster Risk
FEMA National Risk Index assessment · CA
HighComposite Risk Score
National percentile: 99th
San Joaquin County faces high composite natural disaster risk (NRI Risk Index score 98.6, 99th national percentile), driven primarily by drought and earthquake exposure. Expected annual loss across all 18 hazard types is $422M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in San Joaquin County is high, with a National Risk Index score of 98.6 out of 100 — placing it in the 99th national percentile and in the upper tier of natural-disaster risk nationally. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
The county's risk is driven primarily by drought (extended dry periods that stress water supplies and agriculture) at Very High risk — $83M in expected annual loss and about 68.55 events per year; earthquake (ground shaking from sudden movement along geologic faults) at High risk — $184M in expected annual loss and about 0.11 events per year; and riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at High risk — $138M in expected annual loss and about 1.11 events per year. Across all hazards, FEMA estimates $422M in expected annual loss for a population of 779K.
Beyond physical exposure, San Joaquin County has a low social vulnerability rating (how susceptible the population is to harm) and a medium community resilience rating (its capacity to prepare for and recover from disasters). Both measures sit toward the lower end, indicating relatively modest population sensitivity.
The federal record bears this out: San Joaquin County has received 25 federal disaster declarations since 1964, including 10 for flood events and 6 for severe storm events. The most recent was Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides (severe storm), declared in April 2023.
Among 58 California counties, San Joaquin County ranks #17 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Drought | Very High | 68.55 / yr | $83M |
| Earthquake | High | 0.11 / yr | $184M |
| Riverine Flood | High | 1.11 / yr | $138M |
| Heat Wave | High | 6.98 / yr | $11M |
| Lightning | High | 7.70 / yr | $2M |
| Wildfire | Medium | 0.00 / yr | $2M |
| Volcanic Activity | Very Low | 0.00 / yr | $515 |
| Landslide | Very Low | 7.42 / yr | $3K |
| Hail | Low | 0.07 / yr | $316K |
| Tornado | Low | 0.18 / yr | $1M |
| Winter Weather | Low | 0.20 / yr | $49K |
| Strong Wind | Low | 0.05 / yr | $384K |
| Avalanche | Very Low | 0.01 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Cold Wave | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Ice Storm | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
San Joaquin County has received 25 federal disaster declarations since 1964, most recently Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides in April 2023. Most frequent causes: Flood (10), Severe Storm (6), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| April 2023 | Severe Storm | Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| March 2023 | Flood | Severe Winter Storms, Flooding, Landslides, and Mudslides |
| January 2023 | Flood | Severe Winter Storms, Flooding, Landslides, and Mudslides |
| January 2023 | Flood | Severe Winter Storms, Flooding, and Mudslides |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| April 2017 | Flood | Severe Winter Storms, Flooding, and Mudslides |
| June 2006 | Severe Storm | Severe Storms, Flooding, Landslides, and Mudslides |
| February 2006 | Severe Storm | Severe Storms, Flooding, Mudslides, and Landslides |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
Showing the 10 most recent of 25 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for San Joaquin County?
San Joaquin County has a composite FEMA National Risk Index score of 98.6 out of 100, placing it in the High category and the 99th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in San Joaquin County?
The three highest-rated hazards are Drought (Very High, $83M EAL), Earthquake (High, $184M EAL), Riverine Flood (High, $138M EAL). These account for most of the county's expected annual losses.
How does San Joaquin County compare to other California counties?
San Joaquin County ranks #17 of 58 California counties for overall natural disaster risk, with a high rating.
How many federally declared disasters has San Joaquin County had?
FEMA records 25 federal disaster declarations for San Joaquin County since 1964, most often 10 for flood events and 6 for severe storm events. The most recent was Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides, declared in April 2023.
What does Expected Annual Loss (EAL) mean?
EAL is FEMA's estimate of average annual dollar losses from natural hazards, calculated from historical event data and exposure models. San Joaquin County's $422M EAL is a statistical average, not a guarantee for any specific year or address.