Chester County, Pennsylvania: Natural Disaster Risk and History
Chester County, Pennsylvania has a Relatively Moderate natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 91.9 out of 100, higher than about 91% of US counties, with drought, winter storms and heat waves scoring highest of its 18 hazards and $173 million a year in expected losses.
OpenFEMA lists 24 federal disaster declarations that included Chester 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 31 tornadoes touching Chester County from 1950 to 2025.
Live weather alerts for Pennsylvania All official warnings Latest FEMA declarations
Population 534,152 Buildings worth $164 billion Area 767 sq mi Risk rank in Pennsylvania 9 of 67 FIPS 42029
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Drought | Relatively High | 98.6 | $10 million | about 4.9 a year | 196 |
| Winter weather | Very High | 98.4 | $2.3 million | about 12 a year | 230 |
| Heat wave | Relatively Moderate | 95.6 | $11 million | about 9.2 a year | 109 |
| Strong wind | Relatively High | 94.6 | $4.6 million | about 7.2 a year | 274 |
| Inland flooding | Relatively High | 94.3 | $106 million | about 5.5 a year | 153 |
| Lightning | Relatively High | 91.4 | $2.1 million | about 36 a year | 369,108 strikes |
| Earthquake | Relatively Moderate | 90.2 | $8.5 million | about once every 735 years | — |
| Hurricane | Relatively Moderate | 88.7 | $9.6 million | about once every 12 years | 28 |
| Tornado | Relatively Moderate | 88.0 | $9.8 million | about once every 2.2 years | 24 |
| Ice storm | Relatively High | 85.7 | $993,065 | about 1.3 a year | 90 |
| Cold wave | Relatively Moderate | 84.2 | $7.5 million | about once every 1.1 years | 17 |
| Landslide | Relatively Low | 77.8 | $19,727 | about once every 1.5 years | — |
| Hail | Relatively Low | 61.2 | $618,172 | about 2.8 a year | 105 |
| Wildfire | Very Low | 30.7 | $23,200 | rarer than once in 1,000 years | — |
| Coastal flooding | No Rating | 0.0 | — | about once every 83 years | — |
| Avalanche | Not Applicable | — | — | — | — |
| Tsunami | Not Applicable | — | — | — | — |
| 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 24
Most common: Hurricane 7, Flood 6, Severe Storm 5, Snowstorm 4.
| Decade | Declarations | Incident types |
|---|---|---|
| 1960s | 1 | Drought |
| 1970s | 3 | Flood ×3 |
| 1990s | 5 | Snowstorm ×2, Hurricane, Flood, Severe Storm |
| 2000s | 6 | Severe Storm ×4, Hurricane ×2 |
| 2010s | 8 | Hurricane ×3, Snowstorm ×2, Flood ×2, Severe Ice Storm |
| 2020s | 1 | Hurricane |
The last 10
Widest declarations that included Chester 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 31
| Tornadoes touching the county | 31 |
|---|---|
| Strongest-rated | (E)F3 ×2 |
| Peak month | July (6) |
| Deadliest | 5 Sep 1979, F2, 4.1 mi path, 1 killed, 4 injured |
| Longest path | 22 Mar 1955, F3, 9.6 mi path, 1 killed, 0 injured |
| Most recent | 16 Jun 2023, EF1, 1.8 mi path |
| Deaths / injuries on those paths | 3 / 32 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 6 | 17 | 6 | 2 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 3 | 1 | 4 | 3 | 15 | 1 | 2 | 2 |
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 Chester County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Chester County (this page) | — | Relatively Moderate | 91.9 | Drought |
| Delaware County | 30 km | Relatively Moderate | 92.9 | Winter weather |
| Montgomery County | 42 km | Relatively High | 96.8 | Winter weather |
| Lancaster County | 43 km | Relatively High | 95.0 | Winter weather |
| New Castle County, DE | 45 km | Relatively High | 95.3 | Winter weather |
| Cecil County, MD | 47 km | Relatively Low | 58.6 | Drought |
Nearest by distance between county centres. Every county in Pennsylvania, ranked.
Vulnerability and resilience
| Social vulnerability | Very Low 10.6 |
|---|---|
| Community resilience | Very High 85.2 |
| Community risk factor | 0.66 |
| Expected annual loss, all hazards | $173 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 Chester County's main hazards
- Right now: National Weather Service alerts for Pennsylvania · all official warnings on Global Incident Tracker.
- Drought: Drought monitor for Pennsylvania
- Winter weather: Power outages now · Carbon monoxide in winter
- 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 Chester County
What natural disasters is Chester County, Pennsylvania most at risk from?
Chester County, Pennsylvania has a Relatively Moderate natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 91.9 out of 100, higher than about 91% of US counties, with drought, winter storms and heat waves scoring highest of its 18 hazards and $173 million a year in expected losses.
How many federal disaster declarations has Chester County had?
OpenFEMA lists 24 federal disaster declarations that included Chester 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 Chester County?
NOAA's Storm Prediction Center recorded 31 tornadoes touching Chester County from 1950 to 2025. The deadliest: 5 Sep 1979, F2, 4.1 mi path, 1 killed, 4 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.