Delaware County, Pennsylvania: Natural Disaster Risk and History
Delaware County, Pennsylvania has a Relatively Moderate natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 92.9 out of 100, higher than about 92% of US counties, with winter storms, strong winds and heat waves scoring highest of its 18 hazards and $135 million a year in expected losses.
OpenFEMA lists 22 federal disaster declarations that included Delaware County since 1965, not counting 2 for COVID-19; the latest is DR-4618-PA (Remnants of Hurricane Ida, declared 10 September 2021). NOAA's Storm Prediction Center recorded 6 tornadoes touching Delaware County from 1950 to 2025.
Live weather alerts for Pennsylvania All official warnings Latest FEMA declarations
Population 576,366 Buildings worth $133 billion Area 193 sq mi Risk rank in Pennsylvania 7 of 67 FIPS 42045
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Winter weather | Very High | 99.2 | $2.1 million | about 11 a year | 199 |
| Strong wind | Relatively High | 97.7 | $5.2 million | about 6.9 a year | 264 |
| Heat wave | Relatively High | 97.6 | $13 million | about 11 a year | 125 |
| Lightning | Relatively High | 95.6 | $2.1 million | about 36 a year | 324,427 strikes |
| Earthquake | Relatively Moderate | 94.5 | $13 million | about once every 617 years | — |
| Inland flooding | Relatively High | 94.4 | $74 million | about 4.6 a year | 130 |
| Tornado | Relatively High | 92.5 | $9.4 million | about once every 10 years | 6 |
| Cold wave | Relatively High | 91.5 | $8.5 million | about once every 1.3 years | 15 |
| Hurricane | Relatively Moderate | 88.1 | $5.9 million | about once every 11 years | 16 |
| Ice storm | Relatively High | 87.0 | $749,969 | about 1.4 a year | 95 |
| Coastal flooding | Relatively Moderate | 63.6 | $730,166 | about 3.7 a year | — |
| Landslide | Very Low | 59.4 | $2,758 | about once every 6.3 years | — |
| Drought | Relatively Low | 54.2 | $208,692 | about 5.7 a year | 168 |
| Wildfire | Very Low | 27.7 | $13,011 | rarer than once in 1,000 years | — |
| Hail | Very Low | 13.3 | $45,783 | about 2.5 a year | 97 |
| Avalanche | Very Low | 11.4 | $11 | about once every 100 years | 0 |
| Tsunami | Insufficient Data | — | — | — | — |
| Volcanic activity | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 22
Most common: Hurricane 7, Flood 6, Severe Storm 4, Snowstorm 3.
| Decade | Declarations | Incident types |
|---|---|---|
| 1960s | 1 | Drought |
| 1970s | 3 | Flood ×3 |
| 1990s | 5 | Snowstorm ×2, Hurricane, Flood, Severe Storm |
| 2000s | 5 | Severe Storm ×3, Hurricane ×2 |
| 2010s | 7 | Hurricane ×3, Flood ×2, Severe Ice Storm, Snowstorm |
| 2020s | 1 | Hurricane |
The last 10
Widest declarations that included Delaware County
- Hurricane Sandy (2012, EM-3356-PA): 67 Pennsylvania counties designated.
- Hurricane Katrina (2005, EM-3235-PA): 67 Pennsylvania counties designated.
- Tropical Depression Ivan (2004, DR-1557-PA): 67 Pennsylvania counties designated.
Named storms in its declarations: Hurricane Ida (2021), Hurricane Sandy (2012), Tropical Storm Lee (2011), Hurricane Irene (2011), Hurricane Katrina (2005), Tropical Depression Ivan (2004), Tropical Depression Frances (2004), Hurricane Floyd (1999), Tropical Storm Agnes (1972).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Pennsylvania also had 5 statewide declarations with no county list.
Tornado record since 1950 6
| Tornadoes touching the county | 6 |
|---|---|
| Strongest-rated | (E)F2 ×2 |
| Peak month | April (1) |
| Deadliest | 31 Oct 2019, EF2, 0.5 mi path, 0 killed, 2 injured |
| Longest path | 27 Sep 1993, F1, 3 mi path |
| Most recent | 31 Oct 2019, EF2, 0.5 mi path, 0 killed, 2 injured |
| Deaths / injuries on those paths | 0 / 2 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 1 | 3 | 2 | 0 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 0 | 0 | 1 | 0 | 3 | 0 | 2 | 0 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How Delaware County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Delaware County (this page) | — | Relatively Moderate | 92.9 | Winter weather |
| Philadelphia County | 25 km | Very High | 99.6 | Heat wave |
| Chester County | 30 km | Relatively Moderate | 91.9 | Drought |
| Gloucester County, NJ | 32 km | Relatively Moderate | 86.6 | Strong wind |
| Montgomery County | 33 km | Relatively High | 96.8 | Winter weather |
| Salem County, NJ | 37 km | Relatively Low | 76.5 | Coastal flooding |
Nearest by distance between county centres. Every county in Pennsylvania, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Low 33.0 |
|---|---|
| Community resilience | Very High 84.3 |
| Community risk factor | 0.99 |
| Expected annual loss, all hazards | $135 million |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for Delaware County's main hazards
- Right now: National Weather Service alerts for Pennsylvania · all official warnings on Global Incident Tracker.
- Winter weather: Power outages now · Carbon monoxide in winter
- Strong wind: Power outages now
- Heat wave: Heatstroke warning signs
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about Delaware County
What natural disasters is Delaware County, Pennsylvania most at risk from?
Delaware County, Pennsylvania has a Relatively Moderate natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 92.9 out of 100, higher than about 92% of US counties, with winter storms, strong winds and heat waves scoring highest of its 18 hazards and $135 million a year in expected losses.
How many federal disaster declarations has Delaware County had?
OpenFEMA lists 22 federal disaster declarations that included Delaware County since 1965, not counting 2 for COVID-19; the latest is DR-4618-PA (Remnants of Hurricane Ida, declared 10 September 2021). Another 5 Pennsylvania declarations were made statewide without a county list.
How many tornadoes have hit Delaware County?
NOAA's Storm Prediction Center recorded 6 tornadoes touching Delaware County from 1950 to 2025. The deadliest: 31 Oct 2019, EF2, 0.5 mi path, 0 killed, 2 injured (deaths and injuries are for the whole path).
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.