Philadelphia County, Pennsylvania Natural Disaster Risk
FEMA National Risk Index assessment · PA
Very HighComposite Risk Score
National percentile: 100th
Philadelphia County faces very high composite natural disaster risk (NRI Risk Index score 99.6, 100th national percentile), driven primarily by heat wave and cold wave exposure. Expected annual loss across all 18 hazard types is $667M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Philadelphia County is very high, with a National Risk Index score of 99.6 out of 100 — placing it in the 100th national percentile and among the most at-risk counties in the United States. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Risk here concentrates in heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at Very High risk — $256M in expected annual loss and about 11.07 events per year; cold wave (prolonged spells of dangerously low temperatures) at Very High risk — $57M in expected annual loss and about 0.79 events per year; and winter weather (heavy snow, blizzards, and hazardous winter conditions) at Very High risk — $2M in expected annual loss and about 10.54 events per year. Across all hazards, FEMA estimates $667M in expected annual loss for a population of 1.6M.
Beyond physical exposure, Philadelphia County has a very high 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). That combination — a more vulnerable population with limited resilience — can amplify the human cost of any given event.
The county's disaster history tells the same story: Philadelphia County has received 25 federal disaster declarations since 1965, including 8 for hurricane events and 5 for flood events. The most recent was Remnants of Hurricane Ida (hurricane), declared in September 2021.
Among 67 Pennsylvania counties, Philadelphia County ranks #1 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Heat Wave | Very High | 11.07 / yr | $256M |
| Cold Wave | Very High | 0.79 / yr | $57M |
| Winter Weather | Very High | 10.54 / yr | $2M |
| Riverine Flood | Very High | 5.82 / yr | $266M |
| Tornado | High | 0.07 / yr | $21M |
| Earthquake | High | 0.00 / yr | $42M |
| Strong Wind | High | 7.04 / yr | $4M |
| Lightning | High | 35.74 / yr | $2M |
| Hail | High | 2.51 / yr | $2M |
| Hurricane | High | 0.09 / yr | $12M |
| Ice Storm | High | 1.44 / yr | $989K |
| Coastal Flood | High | 3.69 / yr | $3M |
| Landslide | Low | 0.06 / yr | $7K |
| Wildfire | Very Low | 0.00 / yr | $9K |
| Drought | Very Low | 5.76 / yr | $4K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Philadelphia County has received 25 federal disaster declarations since 1965, most recently Remnants of Hurricane Ida in September 2021. Most frequent causes: Hurricane (8), Flood (5), Snowstorm (4).
| Declared | Type | Disaster |
|---|---|---|
| September 2021 | Hurricane | Remnants of Hurricane Ida |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| March 2016 | Snowstorm | Severe Winter Storm and Snowstorm |
| February 2014 | Severe Ice Storm | Severe Winter Storm |
| January 2013 | Hurricane | Hurricane Sandy |
| October 2012 | Hurricane | Hurricane Sandy |
| September 2011 | Flood | Tropical Storm Lee |
| September 2011 | Flood | Remnants of Tropical Storm Lee |
| September 2011 | Hurricane | Hurricane Irene |
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 Philadelphia County?
Philadelphia County has a composite FEMA National Risk Index score of 99.6 out of 100, placing it in the Very High category and the 100th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Philadelphia County?
The three highest-rated hazards are Heat Wave (Very High, $256M EAL), Cold Wave (Very High, $57M EAL), Winter Weather (Very High, $2M EAL). These account for most of the county's expected annual losses.
How does Philadelphia County compare to other Pennsylvania counties?
Philadelphia County ranks #1 of 67 Pennsylvania counties for overall natural disaster risk, with a very high rating.
How many federally declared disasters has Philadelphia County had?
FEMA records 25 federal disaster declarations for Philadelphia County since 1965, most often 8 for hurricane events and 5 for flood events. The most recent was Remnants of Hurricane Ida, declared in September 2021.
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. Philadelphia County's $667M EAL is a statistical average, not a guarantee for any specific year or address.