New Castle County, Delaware: Natural Disaster Risk and History
New Castle County, Delaware has a Relatively High natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 95.3 out of 100, higher than about 95% of US counties, with winter storms, inland (river and flash) flooding and heat waves scoring highest of its 18 hazards and $202 million a year in expected losses.
OpenFEMA lists 15 federal disaster declarations that included New Castle County since 1965, not counting 2 for COVID-19; the latest is DR-4627-DE (Remnants of Hurricane Ida, declared 24 October 2021). NOAA's Storm Prediction Center recorded 28 tornadoes touching New Castle County from 1950 to 2025.
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Population 570,089 Buildings worth $137 billion Area 499 sq mi Risk rank in Delaware 1 of 3 FIPS 10003
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 | 99.5 | $2.5 million | about 1 a year | 197 |
| Inland flooding | Relatively High | 97.6 | $150 million | about 6.6 a year | 184 |
| Heat wave | Relatively Moderate | 95.3 | $7.1 million | about 11 a year | 127 |
| Cold wave | Relatively High | 93.4 | $10 million | about once every 1.3 years | 15 |
| Earthquake | Relatively Moderate | 92.9 | $9.2 million | about once every 617 years | — |
| Ice storm | Relatively High | 89.0 | $913,452 | about once a year | 63 |
| Hurricane | Relatively Moderate | 88.4 | $6.5 million | about once every 11 years | 16 |
| Strong wind | Relatively High | 88.3 | $2.0 million | about 6.3 a year | 217 |
| Tornado | Relatively Moderate | 88.1 | $7.0 million | about once every 3.9 years | 18 |
| Drought | Relatively Moderate | 84.0 | $1.3 million | about 5.9 a year | 196 |
| Coastal flooding | Relatively High | 83.8 | $3.7 million | about 3.7 a year | — |
| Lightning | Relatively Moderate | 81.3 | $847,209 | about 35 a year | 319,315 strikes |
| Landslide | Relatively Low | 76.6 | $11,670 | about once every 7.2 years | — |
| Wildfire | Very Low | 60.6 | $94,808 | rarer than once in 1,000 years | — |
| Hail | Very Low | 24.2 | $97,434 | about 2.3 a year | 89 |
| Avalanche | Not Applicable | — | — | — | — |
| 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 15
Most common: Hurricane 9, Snowstorm 4, Severe Storm 1, Drought 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1960s | 1 | Drought |
| 1990s | 3 | Snowstorm ×2, Hurricane |
| 2000s | 5 | Hurricane ×3, Severe Storm, Snowstorm |
| 2010s | 4 | Hurricane ×3, Snowstorm |
| 2020s | 2 | Hurricane ×2 |
The last 10
Widest declarations that included New Castle County
- Hurricane Sandy (2012, DR-4090-DE): 3 Delaware counties designated.
- Hurricane Sandy (2012, EM-3357-DE): 3 Delaware counties designated.
- Hurricane Irene (2011, EM-3336-DE): 3 Delaware counties designated.
Named storms in its declarations: Hurricane Ida (2021), Tropical Storm Isaias (2020), Hurricane Sandy (2012), Hurricane Irene (2011), Hurricane Katrina (2005), Tropical Storm Henri (2003), Hurricane Isabel (2003), Hurricane Floyd (1999).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Delaware also had 1 statewide declaration with no county list.
Tornado record since 1950 28
| Tornadoes touching the county | 28 |
|---|---|
| Strongest-rated | (E)F3 ×1 |
| Peak month | July (7) |
| Deadliest | 7 Jun 1988, F1, 23 mi path, 0 killed, 30 injured |
| Longest path | 4 Aug 2020, EF2, 35.8 mi path |
| Most recent | 8 Aug 2024, EF1, 1.1 mi path |
| Deaths / injuries on those paths | 0 / 38 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 8 | 12 | 7 | 1 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 2 | 5 | 6 | 4 | 4 | 1 | 2 | 4 |
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 New Castle County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| New Castle County (this page) | — | Relatively High | 95.3 | Winter weather |
| Cecil County, MD | 25 km | Relatively Low | 58.6 | Drought |
| Salem County, NJ | 26 km | Relatively Low | 76.5 | Coastal flooding |
| Delaware County, PA | 44 km | Relatively Moderate | 92.9 | Winter weather |
| Chester County, PA | 45 km | Relatively Moderate | 91.9 | Drought |
| Gloucester County, NJ | 47 km | Relatively Moderate | 86.6 | Strong wind |
Nearest by distance between county centres. Every county in Delaware, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Low 28.5 |
|---|---|
| Community resilience | Very High 83.0 |
| Community risk factor | 0.95 |
| Expected annual loss, all hazards | $202 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 New Castle County's main hazards
- Right now: National Weather Service alerts for Delaware · all official warnings on Global Incident Tracker.
- Winter weather: Power outages now · Carbon monoxide in winter
- Inland flooding: Flood safety: why shallow water kills · Floods recorded
- 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 New Castle County
What natural disasters is New Castle County, Delaware most at risk from?
New Castle County, Delaware has a Relatively High natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 95.3 out of 100, higher than about 95% of US counties, with winter storms, inland (river and flash) flooding and heat waves scoring highest of its 18 hazards and $202 million a year in expected losses.
How many federal disaster declarations has New Castle County had?
OpenFEMA lists 15 federal disaster declarations that included New Castle County since 1965, not counting 2 for COVID-19; the latest is DR-4627-DE (Remnants of Hurricane Ida, declared 24 October 2021). Another 1 Delaware declarations were made statewide without a county list.
How many tornadoes have hit New Castle County?
NOAA's Storm Prediction Center recorded 28 tornadoes touching New Castle County from 1950 to 2025. The deadliest: 7 Jun 1988, F1, 23 mi path, 0 killed, 30 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.