Delaware County, Pennsylvania Natural Disaster Risk
FEMA National Risk Index assessment · PA
MediumComposite Risk Score
National percentile: 93th
Delaware County faces medium composite natural disaster risk (NRI Risk Index score 92.9, 93th national percentile), driven primarily by winter weather and strong wind exposure. Expected annual loss across all 18 hazard types is $135M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Delaware County carries a medium composite natural disaster risk, with a National Risk Index score of 92.9 out of 100 — placing it in the 93rd national percentile and near the national midpoint for natural-disaster risk. 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 winter weather (heavy snow, blizzards, and hazardous winter conditions) at Very High risk — $2M in expected annual loss and about 10.49 events per year; strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at High risk — $5M in expected annual loss and about 6.94 events per year; and heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at High risk — $13M in expected annual loss and about 11.06 events per year. Across all hazards, FEMA estimates $135M in expected annual loss for a population of 576K.
Beyond physical exposure, Delaware County has a low social vulnerability rating (how susceptible the population is to harm) and a very high community resilience rating (its capacity to prepare for and recover from disasters). A less vulnerable population paired with strong resilience helps the community absorb and recover from events.
The federal record bears this out: Delaware County has received 24 federal disaster declarations since 1965, including 7 for hurricane events and 6 for flood events. The most recent was Remnants of Hurricane Ida (hurricane), declared in September 2021.
Among 67 Pennsylvania counties, Delaware County ranks #7 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Winter Weather | Very High | 10.49 / yr | $2M |
| Strong Wind | High | 6.94 / yr | $5M |
| Heat Wave | High | 11.06 / yr | $13M |
| Lightning | High | 35.98 / yr | $2M |
| Earthquake | Medium | 0.00 / yr | $13M |
| Riverine Flood | High | 4.64 / yr | $74M |
| Tornado | High | 0.10 / yr | $9M |
| Cold Wave | High | 0.79 / yr | $9M |
| Hurricane | Medium | 0.09 / yr | $6M |
| Ice Storm | High | 1.41 / yr | $750K |
| Coastal Flood | Medium | 3.69 / yr | $730K |
| Landslide | Very Low | 0.16 / yr | $3K |
| Drought | Low | 5.71 / yr | $209K |
| Wildfire | Very Low | 0.00 / yr | $13K |
| Hail | Very Low | 2.47 / yr | $46K |
| Avalanche | Very Low | 0.01 / yr | $11 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Delaware County has received 24 federal disaster declarations since 1965, most recently Remnants of Hurricane Ida in September 2021. Most frequent causes: Hurricane (7), Flood (6), Severe Storm (4).
| Declared | Type | Disaster |
|---|---|---|
| September 2021 | Hurricane | Remnants of Hurricane Ida |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| February 2014 | Severe Ice Storm | Severe Winter Storm |
| October 2012 | Hurricane | Hurricane Sandy |
| September 2011 | Flood | Tropical Storm Lee |
| September 2011 | Flood | Remnants of Tropical Storm Lee |
| September 2011 | Hurricane | Hurricane Irene |
| August 2011 | Hurricane | Hurricane Irene |
| April 2010 | Snowstorm | Severe Winter Storms and Snowstorms |
Showing the 10 most recent of 24 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Delaware County?
Delaware County has a composite FEMA National Risk Index score of 92.9 out of 100, placing it in the Medium category and the 93th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Delaware County?
The three highest-rated hazards are Winter Weather (Very High, $2M EAL), Strong Wind (High, $5M EAL), Heat Wave (High, $13M EAL). These account for most of the county's expected annual losses.
How does Delaware County compare to other Pennsylvania counties?
Delaware County ranks #7 of 67 Pennsylvania counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Delaware County had?
FEMA records 24 federal disaster declarations for Delaware County since 1965, most often 7 for hurricane events and 6 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. Delaware County's $135M EAL is a statistical average, not a guarantee for any specific year or address.