Hillsborough County, New Hampshire Natural Disaster Risk
FEMA National Risk Index assessment · NH
MediumComposite Risk Score
National percentile: 90th
Hillsborough County faces medium composite natural disaster risk (NRI Risk Index score 89.8, 90th national percentile), driven primarily by ice storm and lightning exposure. Expected annual loss across all 18 hazard types is $120M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Hillsborough County is medium, with a National Risk Index score of 89.8 out of 100 — placing it in the 90th national percentile and near the national midpoint for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Risk here concentrates in ice storm (freezing rain that coats surfaces in heavy, damaging ice) at Very High risk — $3M in expected annual loss and about 2.14 events per year; lightning (electrical discharges from storms that ignite fires and cause casualties) at High risk — $2M in expected annual loss and about 21.14 events per year; and hurricane (tropical cyclones bringing extreme wind, rain, and storm surge) at Medium risk — $18M in expected annual loss and about 0.11 events per year. Across all hazards, FEMA estimates $120M in expected annual loss for a population of 423K.
Beyond physical exposure, Hillsborough County has a very low social vulnerability rating (how susceptible the population is to harm) and a 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.
History supports the rating: Hillsborough County has received 31 federal disaster declarations since 1973, including 13 for severe storm events and 6 for snowstorm events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 10 New Hampshire counties, Hillsborough County ranks #1 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Ice Storm | Very High | 2.14 / yr | $3M |
| Lightning | High | 21.14 / yr | $2M |
| Hurricane | Medium | 0.11 / yr | $18M |
| Riverine Flood | Medium | 1.68 / yr | $76M |
| Earthquake | Low | 0.00 / yr | $6M |
| Winter Weather | High | 18.54 / yr | $486K |
| Strong Wind | High | 1.05 / yr | $3M |
| Landslide | Low | 0.96 / yr | $39K |
| Tornado | Medium | 0.16 / yr | $7M |
| Heat Wave | Low | 3.76 / yr | $2M |
| Wildfire | Low | 0.00 / yr | $204K |
| Cold Wave | Medium | 1.72 / yr | $3M |
| Drought | Low | 3.95 / yr | $357K |
| Hail | Low | 2.37 / yr | $473K |
| Avalanche | Very Low | 0.01 / yr | $28 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Hillsborough County has received 31 federal disaster declarations since 1973, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Severe Storm (13), Snowstorm (6), Flood (5).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| March 2015 | Severe Storm | Severe Winter Storm and Snowstorm |
| March 2013 | Severe Storm | Severe Winter Storm and Snowstorm |
| October 2012 | Hurricane | Hurricane Sandy |
| December 2011 | Severe Storm | Severe Storm and Snowstorm |
| November 2011 | Severe Storm | Severe Storm |
| August 2011 | Hurricane | Hurricane Irene |
| May 2010 | Severe Storm | Severe Storms and Flooding |
| March 2010 | Severe Storm | Severe Winter Storm |
Showing the 10 most recent of 31 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Hillsborough County?
Hillsborough County has a composite FEMA National Risk Index score of 89.8 out of 100, placing it in the Medium category and the 90th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Hillsborough County?
The three highest-rated hazards are Ice Storm (Very High, $3M EAL), Lightning (High, $2M EAL), Hurricane (Medium, $18M EAL). These account for most of the county's expected annual losses.
How does Hillsborough County compare to other New Hampshire counties?
Hillsborough County ranks #1 of 10 New Hampshire counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Hillsborough County had?
FEMA records 31 federal disaster declarations for Hillsborough County since 1973, most often 13 for severe storm events and 6 for snowstorm events. The most recent was Covid-19 Pandemic, declared in April 2020.
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. Hillsborough County's $120M EAL is a statistical average, not a guarantee for any specific year or address.