Philadelphia survival atlas
Philadelphia County, Pennsylvania
Philadelphia’s biggest natural hazards are inland flooding, heat waves and cold waves. In FEMA’s National Risk Index they make up 86% of the natural-hazard risk for Philadelphia County, home to all of Philadelphia’s 1.6 million residents. FEMA rates the county’s overall risk Very High. Here is what to do for each, step by step.
- People
- 1,574,281 Census estimate, July 1, 2025. No. 6 in the U.S.
- County
- Philadelphia County All of Philadelphia’s residents. FEMA rates counties, not cities.
- Overall risk
- Very High Score 99.58 of 100. No. 7 of the 10 largest U.S. cities.
- Expected loss
- $667 million A year, from all 18 natural hazards (FEMA estimate).
- Top 3 hazards
- 86% of the county’s risk comes from these three: Inland flooding · Heat wave · Cold wave.
What to do for Philadelphia’s top hazards
The one rule to remember, then the first steps, word for word from our guides. Each guide lists its sources.
Inland flooding
FEMA score 99.58: higher than 99.5% of U.S. counties. Expected loss $266 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 99.96: higher than 99.9% of U.S. counties. Expected loss $256 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.
Cold wave
FEMA score 99.80: higher than 99.8% of U.S. counties. Expected loss $57.0 million a year.
- One warm room at home. Never heat with an oven or a grill.
- Signs: shivering, confusion, fumbling hands, slurred speech, drowsiness.
- Get them somewhere warm. Take off wet clothing.
All 18 natural hazards in Philadelphia, ranked
Ranked by each hazard’s share of Philadelphia 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 | Inland flooding | 40% | Very High | 99.58 | $266 million | Turn around, don't drown. |
| 2 | Heat wave | 38% | Very High | 99.96 | $256 million | Get somewhere cool. Check on anyone who lives alone. |
| 3 | Cold wave | 8.6% | Very High | 99.80 | $57.0 million | One warm room. Never heat with an oven or a grill. |
| 4 | Earthquake | 6.2% | Relatively High | 98.28 | $41.6 million | Drop. Cover. Hold on. |
| 5 | Tornado | 3.2% | Relatively High | 98.66 | $21.1 million | Lowest floor, interior room, cover your head. |
| 6 | Hurricane | 1.8% | Relatively High | 94.28 | $12.0 million | Know your evacuation zone. Told to go? Go early. |
| 7 | Strong wind | 0.5% | Relatively High | 97.86 | $3.5 million | Shelter in an interior room, away from windows. |
| 8 | Coastal flooding | 0.4% | Relatively High | 85.40 | $2.8 million | Run from the water. Hide from the wind. |
| 9 | Hail | 0.3% | Relatively High | 95.13 | $2.1 million | Get indoors, away from windows. |
| 10 | Winter weather | 0.3% | Very High | 99.77 | $1.9 million | Stay in your shelter, or stay with your car. |
| 11 | Lightning | 0.2% | Relatively High | 96.24 | $1.5 million | When thunder roars, go indoors. |
| 12 | Ice storm | 0.1% | Relatively High | 94.16 | $989,000 | Stay off the roads. One warm room. |
| 13 | Wildfire | <0.1% | Very Low | 28.68 | $9,000 | Leave early. Know two ways out. |
| 14 | Landslide | <0.1% | Relatively Low | 76.33 | $7,000 | Follow local alerts. Leave when officials say so. |
| 15 | Drought | <0.1% | Very Low | 21.66 | $4,000 | Store water now: 1 gallon per person per day. |
| – | Avalanche | – | Not applicable | – | – | Check your local avalanche center before backcountry travel. |
| – | Tsunami | – | Insufficient data | – | – | Strong or long shaking near the sea: go high now. |
| – | Volcanic activity | – | Not applicable | – | – | Evacuate early. In ashfall, stay in and wear an N95. |
Source // FEMA National Risk Index v1.20 (December 2025), county 42101. 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.
- Philadelphia County is rated Very High for social vulnerability and Relatively Moderate for community resilience. Both feed into its overall rating.
Questions people ask
What natural disasters is Philadelphia most at risk for?
Philadelphia’s biggest natural hazards are inland flooding, heat waves and cold waves. In FEMA’s National Risk Index they make up 86% of the natural-hazard risk for Philadelphia County, home to all of Philadelphia’s 1.6 million residents. FEMA rates the county’s overall risk Very High.
How does FEMA rate Philadelphia’s overall disaster risk?
FEMA’s National Risk Index rates the overall risk of Philadelphia County Very High, with a score of 99.58 out of 100. The score is a percentile: Philadelphia County’s overall risk is higher than 99.5% of U.S. counties. Expected losses from natural hazards there average $667 million a year.
What should I do first to get ready in Philadelphia?
Write down your top three: inland flooding, heat waves and cold 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 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)
- Steps: What to do in a winter storm or blizzard (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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