New Castle County, Delaware Natural Disaster Risk
FEMA National Risk Index assessment · DE
HighComposite Risk Score
National percentile: 95th
New Castle County faces high composite natural disaster risk (NRI Risk Index score 95.3, 95th national percentile), driven primarily by winter weather and riverine flood exposure. Expected annual loss across all 18 hazard types is $202M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates New Castle County at high composite risk, with a National Risk Index score of 95.3 out of 100 — placing it in the 95th national percentile and in the upper tier of natural-disaster risk nationally. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of New Castle County's expected losses come from winter weather (heavy snow, blizzards, and hazardous winter conditions) at Very High risk — $2M in expected annual loss and about 10.37 events per year; riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at High risk — $150M in expected annual loss and about 6.57 events per year; and heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at Medium risk — $7M in expected annual loss and about 11.16 events per year. Across all hazards, FEMA estimates $202M in expected annual loss for a population of 570K.
Beyond physical exposure, New Castle 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: New Castle County has received 17 federal disaster declarations since 1965, including 9 for hurricane events and 4 for snowstorm events. The most recent was Remnants of Hurricane Ida (hurricane), declared in October 2021.
Among 3 Delaware counties, New Castle County ranks #1 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Winter Weather | Very High | 10.37 / yr | $2M |
| Riverine Flood | High | 6.57 / yr | $150M |
| Heat Wave | Medium | 11.16 / yr | $7M |
| Cold Wave | High | 0.79 / yr | $10M |
| Earthquake | Medium | 0.00 / yr | $9M |
| Ice Storm | High | 1.03 / yr | $913K |
| Hurricane | Medium | 0.09 / yr | $6M |
| Strong Wind | High | 6.32 / yr | $2M |
| Tornado | Medium | 0.26 / yr | $7M |
| Drought | Medium | 5.90 / yr | $1M |
| Coastal Flood | High | 3.69 / yr | $4M |
| Lightning | Medium | 35.11 / yr | $847K |
| Landslide | Low | 0.14 / yr | $12K |
| Wildfire | Very Low | 0.00 / yr | $95K |
| Hail | Very Low | 2.28 / yr | $97K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
New Castle County has received 17 federal disaster declarations since 1965, most recently Remnants of Hurricane Ida in October 2021. Most frequent causes: Hurricane (9), Snowstorm (4), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| October 2021 | Hurricane | Remnants of Hurricane Ida |
| October 2020 | Hurricane | Tropical Storm Isaias |
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| November 2012 | Hurricane | Hurricane Sandy |
| October 2012 | Hurricane | Hurricane Sandy |
| August 2011 | Hurricane | Hurricane Irene |
| March 2010 | Snowstorm | Severe Winter Storms and Snowstorms |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| November 2004 | Severe Storm | Severe Storms, Tornadoes, and Flooding From the Remnants of |
Showing the 10 most recent of 17 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for New Castle County?
New Castle County has a composite FEMA National Risk Index score of 95.3 out of 100, placing it in the High category and the 95th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in New Castle County?
The three highest-rated hazards are Winter Weather (Very High, $2M EAL), Riverine Flood (High, $150M EAL), Heat Wave (Medium, $7M EAL). These account for most of the county's expected annual losses.
How does New Castle County compare to other Delaware counties?
New Castle County ranks #1 of 3 Delaware counties for overall natural disaster risk, with a high rating.
How many federally declared disasters has New Castle County had?
FEMA records 17 federal disaster declarations for New Castle County since 1965, most often 9 for hurricane events and 4 for snowstorm events. The most recent was Remnants of Hurricane Ida, declared in October 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. New Castle County's $202M EAL is a statistical average, not a guarantee for any specific year or address.