Merrimack County, New Hampshire: Natural Disaster Risk and History
Merrimack County, New Hampshire has a Relatively Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 78.2 out of 100, higher than about 78% of US counties, with ice storms, lightning and inland (river and flash) flooding scoring highest of its 18 hazards and $49 million a year in expected losses.
OpenFEMA lists 27 federal disaster declarations that included Merrimack County since 1973, not counting 2 for COVID-19; the latest is DR-4355-NH (Severe Storm and Flooding, declared 2 January 2018). NOAA's Storm Prediction Center recorded 7 tornadoes touching Merrimack County from 1950 to 2025.
Live weather alerts for New Hampshire All official warnings Latest FEMA declarations
Population 153,727 Buildings worth $31 billion Area 965 sq mi Risk rank in New Hampshire 4 of 10 FIPS 33013
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Ice storm | Relatively High | 89.8 | $1.1 million | about 1.8 a year | 124 |
| Lightning | Relatively High | 89.2 | $1.4 million | about 21 a year | 87,649 strikes |
| Inland flooding | Relatively Moderate | 85.8 | $34 million | about 2.6 a year | 73 |
| Hurricane | Relatively Moderate | 84.8 | $4.5 million | about once every 12 years | 32 |
| Landslide | Relatively Low | 81.1 | $22,620 | about 1.3 a year | — |
| Winter weather | Relatively Moderate | 80.4 | $268,476 | about 19 a year | 363 |
| Earthquake | Relatively Low | 76.1 | $1.5 million | about once every 606 years | — |
| Heat wave | Relatively Low | 70.6 | $1.2 million | about 3.4 a year | 62 |
| Drought | Relatively Low | 58.8 | $329,315 | about 2.2 a year | 154 |
| Tornado | Relatively Low | 56.2 | $1.9 million | about once every 7.8 years | 4 |
| Cold wave | Relatively Low | 53.8 | $1.4 million | about 1.7 a year | 33 |
| Strong wind | Relatively Moderate | 52.5 | $748,178 | about once every 1.1 years | 35 |
| Hail | Relatively Low | 37.2 | $202,124 | about 2.1 a year | 81 |
| Wildfire | Very Low | 35.2 | $24,357 | rarer than once in 1,000 years | — |
| Avalanche | Very Low | 28.5 | $119 | about once every 100 years | 0 |
| Coastal flooding | 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 27
Most common: Severe Storm 12, Snowstorm 5, Flood 5, Hurricane 4.
| Decade | Declarations | Incident types |
|---|---|---|
| 1970s | 1 | Flood |
| 1980s | 1 | Flood |
| 1990s | 6 | Flood ×3, Severe Storm ×2, Snowstorm |
| 2000s | 12 | Severe Storm ×6, Snowstorm ×4, Severe Ice Storm, Hurricane |
| 2010s | 7 | Severe Storm ×4, Hurricane ×3 |
The last 10
Widest declarations that included Merrimack County
- Hurricane Sandy (2012, EM-3360-NH): 10 New Hampshire counties designated.
- Severe Storm (2011, EM-3344-NH): 10 New Hampshire counties designated.
- Hurricane Irene (2011, EM-3333-NH): 10 New Hampshire counties designated.
Named storms in its declarations: Hurricane Sandy (2012), Tropical Storm Irene (2011), Hurricane Irene (2011), Hurricane Katrina (2005).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. New Hampshire also had 1 statewide declaration with no county list.
Tornado record since 1950 7
| Tornadoes touching the county | 7 |
|---|---|
| Strongest-rated | (E)F2 ×2 |
| Peak month | July (4) |
| Deadliest | 24 Jul 2008, EF2, 50.5 mi path, 1 killed, 2 injured |
| Longest path | 24 Jul 2008, EF2, 50.5 mi path, 1 killed, 2 injured |
| Most recent | 4 May 2018, EF1, 37.6 mi path |
| Deaths / injuries on those paths | 1 / 12 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 1 | 4 | 2 | 0 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 0 | 1 | 2 | 0 | 1 | 1 | 2 | 0 |
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 Merrimack County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Merrimack County (this page) | — | Relatively Low | 78.2 | Ice storm |
| Belknap County | 32 km | Relatively Low | 57.4 | Lightning |
| Hillsborough County | 43 km | Relatively Moderate | 89.8 | Ice storm |
| Sullivan County | 44 km | Very Low | 37.6 | Landslide |
| Strafford County | 53 km | Relatively Low | 64.1 | Ice storm |
| Rockingham County | 56 km | Relatively Moderate | 85.8 | Coastal flooding |
Nearest by distance between county centres. Every county in New Hampshire, ranked.
Vulnerability and resilience
| Social vulnerability | Very Low 14.9 |
|---|---|
| Community resilience | Very High 80.8 |
| Community risk factor | 0.83 |
| Expected annual loss, all hazards | $49 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 Merrimack County's main hazards
- Right now: National Weather Service alerts for New Hampshire · all official warnings on Global Incident Tracker.
- Ice storm: Power outages now · Carbon monoxide in winter
- Lightning: Weather alerts for New Hampshire
- Inland flooding: Flood safety: why shallow water kills · Floods recorded
- 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 Merrimack County
What natural disasters is Merrimack County, New Hampshire most at risk from?
Merrimack County, New Hampshire has a Relatively Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 78.2 out of 100, higher than about 78% of US counties, with ice storms, lightning and inland (river and flash) flooding scoring highest of its 18 hazards and $49 million a year in expected losses.
How many federal disaster declarations has Merrimack County had?
OpenFEMA lists 27 federal disaster declarations that included Merrimack County since 1973, not counting 2 for COVID-19; the latest is DR-4355-NH (Severe Storm and Flooding, declared 2 January 2018). Another 1 New Hampshire declarations were made statewide without a county list.
How many tornadoes have hit Merrimack County?
NOAA's Storm Prediction Center recorded 7 tornadoes touching Merrimack County from 1950 to 2025. The deadliest: 24 Jul 2008, EF2, 50.5 mi path, 1 killed, 2 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.