Nantucket County, Massachusetts Natural Disaster Risk
FEMA National Risk Index assessment · MA
Very LowComposite Risk Score
National percentile: 39th
Nantucket County faces very low composite natural disaster risk (NRI Risk Index score 38.7, 39th national percentile), driven primarily by hurricane and coastal flood exposure. Expected annual loss across all 18 hazard types is $23M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Nantucket County is very low, with a National Risk Index score of 38.7 out of 100 — placing it in the 39th national percentile and among the lowest-risk counties in the country. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of Nantucket County's expected losses come from hurricane (tropical cyclones bringing extreme wind, rain, and storm surge) at Medium risk — $17M in expected annual loss and about 0.20 events per year; coastal flood (seawater inundation from storm surge, high tides, and rising sea levels) at Medium risk — $2M in expected annual loss and about 3.69 events per year; and earthquake (ground shaking from sudden movement along geologic faults) at Very Low risk — $65K in expected annual loss and about 0.00 events per year. Across all hazards, FEMA estimates $23M in expected annual loss for a population of 14K.
Beyond physical exposure, Nantucket County has a very 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: Nantucket County has received 20 federal disaster declarations since 1972, including 7 for hurricane events and 4 for snowstorm events. The most recent was Hurricane Lee (hurricane), declared in September 2023.
Among 14 Massachusetts counties, Nantucket County ranks #13 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Hurricane | Medium | 0.20 / yr | $17M |
| Coastal Flood | Medium | 3.69 / yr | $2M |
| Earthquake | Very Low | 0.00 / yr | $65K |
| Drought | Very Low | 1.11 / yr | $12K |
| Riverine Flood | Very Low | 0.25 / yr | $4M |
| Wildfire | Very Low | 0.00 / yr | $8K |
| Lightning | Very Low | 14.42 / yr | $36K |
| Cold Wave | Very Low | 0.32 / yr | $16K |
| Tornado | Very Low | 0.01 / yr | $25K |
| Hail | Very Low | 0.17 / yr | $17K |
| Landslide | Very Low | 0.01 / yr | $4 |
| Strong Wind | Very Low | 0.08 / yr | $17K |
| Winter Weather | Very Low | 5.84 / yr | $2K |
| Ice Storm | Very Low | 0.01 / yr | $162 |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Heat Wave | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Nantucket County has received 20 federal disaster declarations since 1972, most recently Hurricane Lee in September 2023. Most frequent causes: Hurricane (7), Snowstorm (4), Severe Storm (3).
| Declared | Type | Disaster |
|---|---|---|
| September 2023 | Hurricane | Hurricane Lee |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| June 2018 | Severe Storm | Severe Winter Storm and Flooding |
| April 2015 | Severe Storm | Severe Winter Storm, Snowstorm, and Flooding |
| April 2013 | Severe Storm | Severe Winter Storm, Snowstorm, and Flooding |
| December 2012 | Hurricane | Hurricane Sandy |
| October 2012 | Hurricane | Hurricane Sandy |
| August 2011 | Hurricane | Hurricane Irene |
| September 2010 | Hurricane | Hurricane Earl |
Showing the 10 most recent of 20 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Nantucket County?
Nantucket County has a composite FEMA National Risk Index score of 38.7 out of 100, placing it in the Very Low category and the 39th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Nantucket County?
The three highest-rated hazards are Hurricane (Medium, $17M EAL), Coastal Flood (Medium, $2M EAL), Earthquake (Very Low, $65K EAL). These account for most of the county's expected annual losses.
How does Nantucket County compare to other Massachusetts counties?
Nantucket County ranks #13 of 14 Massachusetts counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Nantucket County had?
FEMA records 20 federal disaster declarations for Nantucket County since 1972, most often 7 for hurricane events and 4 for snowstorm events. The most recent was Hurricane Lee, declared in September 2023.
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. Nantucket County's $23M EAL is a statistical average, not a guarantee for any specific year or address.