San Jose survival atlas
Santa Clara County, California
San Jose’s biggest natural hazards are earthquakes, inland flooding and heat waves. In FEMA’s National Risk Index they make up 98% of the natural-hazard risk for Santa Clara County, home to all of San Jose’s 989,814 residents. FEMA rates the county’s overall risk Very High. Here is what to do for each, step by step.
- People
- 989,814 Census estimate, July 1, 2025. No. 13 in the U.S.
- County
- Santa Clara County All of San Jose’s residents. FEMA rates counties, not cities.
- Overall risk
- Very High Score 99.74 of 100. No. 5 of the 30 largest U.S. cities.
- Expected loss
- $2.0 billion A year, from all 18 natural hazards (FEMA estimate).
- Top 3 hazards
- 98% of the county’s risk comes from these three: Earthquake · Inland flooding · Heat wave.
What to do for San Jose’s top hazards
The one rule to remember, then the first steps, word for word from our guides. Each guide lists its sources.
Earthquake
FEMA score 99.93: higher than 99.9% of U.S. counties. Expected loss $1.2 billion a year.
- Drop to your hands and knees.
- Cover your head and neck, under a sturdy table if one is close.
- Hold on until the shaking stops. Don't run outside or stand in a doorway.
Inland flooding
FEMA score 99.77: higher than 99.7% of U.S. counties. Expected loss $720 million a year.
- Get to high ground now.
- Never walk, swim or drive into floodwater. 6 inches of moving water can knock you down; 12 inches carries away most cars.
- Car stalls in rising water: get out to higher ground if you safely can. Trapped in fast water: stay inside; if water rises inside, get on the roof.
Heat wave
FEMA score 98.58: higher than 98.5% of U.S. counties. Expected loss $23.5 million a year.
- Use air conditioning, or go to a library, mall or cooling center.
- Heat stroke signs: confusion, slurred speech, collapse; hot, dry or soaked skin; 103°F or higher.
- Call 911.
All 18 natural hazards in San Jose, ranked
Ranked by each hazard’s share of Santa Clara County’s risk in FEMA’s National Risk Index. The score compares the county with every other U.S. county for that one hazard.
| # | Hazard | Share of risk | FEMA rating | Score | Expected loss a year | The rule |
|---|---|---|---|---|---|---|
| 1 | Earthquake | 60% | Very High | 99.93 | $1.2 billion | Drop. Cover. Hold on. |
| 2 | Inland flooding | 37% | Very High | 99.77 | $720 million | Turn around, don't drown. |
| 3 | Heat wave | 1.2% | Relatively High | 98.58 | $23.5 million | Get somewhere cool. Check on anyone who lives alone. |
| 4 | Drought | 0.5% | Relatively High | 99.20 | $10.6 million | Store water now: 1 gallon per person per day. |
| 5 | Wildfire | 0.5% | Relatively Moderate | 97.39 | $10.2 million | Leave early. Know two ways out. |
| 6 | Coastal flooding | 0.3% | Relatively High | 88.80 | $6.7 million | Run from the water. Hide from the wind. |
| 7 | Landslide | 0.3% | Relatively High | 99.74 | $4.9 million | Follow local alerts. Leave when officials say so. |
| 8 | Tornado | <0.1% | Relatively Low | 55.78 | $1.8 million | Lowest floor, interior room, cover your head. |
| 9 | Lightning | <0.1% | Relatively Low | 46.94 | $254,000 | When thunder roars, go indoors. |
| 10 | Hail | <0.1% | Relatively Low | 37.53 | $197,000 | Large hail coming? Get inside a sturdy building and away from the windows. |
| 11 | Tsunami | <0.1% | Very Low | 18.46 | $142,000 | Strong or long shaking near the sea: go high now. |
| 12 | Strong wind | <0.1% | Very Low | 9.35 | $81,000 | Shelter in an interior room, away from windows. |
| 13 | Winter weather | <0.1% | Very Low | 3.08 | $2,000 | Stay in your shelter, or stay with your car. |
| 14 | Avalanche | <0.1% | Very Low | 13.01 | $17 | Check your local avalanche center before backcountry travel. |
| 15 | Volcanic activity | <0.1% | Very Low | 14.98 | $0 | Evacuate early. In ashfall, stay in and wear an N95. |
| – | Cold wave | – | No rating | – | – | One warm room. Never heat with an oven or a grill. |
| – | Hurricane | – | Not applicable | – | – | Know your evacuation zone. Told to go? Go early. |
| – | Ice storm | – | Not applicable | – | – | Stay off the roads. One warm room. |
Source // FEMA National Risk Index v1.20 (December 2025), county 06085. Rules: SOS.city survival guides.
How to read these numbers
- Share of risk. For each hazard, FEMA estimates the loss each year to buildings, people and farms, then adjusts it for social vulnerability and community resilience. The county’s overall risk is the sum of all 18, so the share shows how much of it each hazard carries.
- Score. A percentile from 0 to 100. A score of 99.5 means the county’s risk for that hazard is higher than 99.5% of U.S. counties.
- Rating. FEMA sorts counties into five groups, from Very Low to Very High.
- Big places rank high. Expected losses grow with the number of people and buildings exposed, so large urban counties rank high on many hazards. A high rating means plan for it, not that it will happen this year.
- County, not street. These ratings cover the whole county. For flood risk at your address, look it up on the FEMA Flood Map Service Center.
- Santa Clara County is rated Very Low for social vulnerability and Relatively High for community resilience. Both feed into its overall rating.
Questions people ask
What natural disasters is San Jose most at risk for?
San Jose’s biggest natural hazards are earthquakes, inland flooding and heat waves. In FEMA’s National Risk Index they make up 98% of the natural-hazard risk for Santa Clara County, home to all of San Jose’s 989,814 residents. FEMA rates the county’s overall risk Very High.
How does FEMA rate San Jose’s overall disaster risk?
FEMA’s National Risk Index rates the overall risk of Santa Clara County Very High, with a score of 99.74 out of 100. The score is a percentile: Santa Clara County’s overall risk is higher than 99.7% of U.S. counties. Expected losses from natural hazards there average $2.0 billion a year.
What should I do first to get ready in San Jose?
Write down your top three: earthquakes, inland flooding and heat waves. Turn on Emergency Alerts on every phone and sign up for your county’s alerts. Store water: 1 gallon per person per day for at least 3 days, 2 weeks if you can.
Sources
Every number on this page comes from these public datasets. We check them when we review the page.
- FEMA: National Risk Index data, county table (v1.20, December 2025)
- FEMA: National Risk Index frequently asked questions (December 2025)
- FEMA: National Risk Index for Natural Hazards
- U.S. Census Bureau: City and town population totals, 2020–2025 (Vintage 2025)
- Steps: What to do during an earthquake (SOS.city guide; its sources are listed on the page)
- Steps: What to do in a flood or flash flood (SOS.city guide; its sources are listed on the page)
- Steps: What to do in extreme heat and heat stroke (SOS.city guide; its sources are listed on the page)
General safety information, not medical advice. In an emergency, call 911 and follow local officials.
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