Mercer County, New Jersey: Natural Disaster Risk and History
Mercer County, New Jersey has a Relatively High natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 95.4 out of 100, higher than about 95% of US counties, with strong winds, winter storms and inland (river and flash) flooding scoring highest of its 18 hazards and $176 million a year in expected losses.
OpenFEMA lists 26 federal disaster declarations that included Mercer County since 1965, not counting 2 for COVID-19; the latest is DR-4614-NJ (Remnants of Hurricane Ida, declared 5 September 2021). NOAA's Storm Prediction Center recorded 13 tornadoes touching Mercer County from 1950 to 2025.
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Population 386,483 Buildings worth $93 billion Area 231 sq mi Risk rank in New Jersey 9 of 21 FIPS 34021
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Strong wind | Very High | 99.5 | $13 million | about 7 a year | 267 |
| Winter weather | Very High | 97.7 | $1.1 million | about 11 a year | 202 |
| Inland flooding | Relatively High | 97.2 | $114 million | about 3.6 a year | 102 |
| Ice storm | Very High | 96.3 | $1.9 million | about 1.1 a year | 74 |
| Heat wave | Relatively Moderate | 95.8 | $6.8 million | about 11 a year | 123 |
| Hurricane | Relatively High | 94.6 | $18 million | about once every 8.7 years | 28 |
| Earthquake | Relatively Moderate | 94.0 | $11 million | about once every 532 years | — |
| Lightning | Relatively High | 93.5 | $1.5 million | about 34 a year | 186,597 strikes |
| Cold wave | Relatively Moderate | 85.2 | $4.8 million | about once every 1.2 years | 16 |
| Tornado | Relatively Moderate | 81.9 | $4.1 million | about once every 11 years | 15 |
| Wildfire | Relatively Low | 73.4 | $215,926 | rarer than once in 1,000 years | — |
| Drought | Relatively Low | 62.1 | $304,640 | about 3.2 a year | 119 |
| Coastal flooding | Relatively Low | 56.8 | $329,235 | about 6.2 a year | — |
| Landslide | Very Low | 53.5 | $1,608 | about once every 15 years | — |
| Hail | Very Low | 29.5 | $110,217 | about 2.4 a year | 91 |
| Avalanche | 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 26
Most common: Hurricane 9, Severe Storm 7, Snowstorm 4, Drought 2.
| Decade | Declarations | Incident types |
|---|---|---|
| 1960s | 1 | Drought |
| 1970s | 2 | Flood ×2 |
| 1980s | 1 | Drought |
| 1990s | 4 | Hurricane ×2, Snowstorm ×2 |
| 2000s | 8 | Severe Storm ×4, Hurricane, Snowstorm, Fire, Other |
| 2010s | 8 | Hurricane ×4, Severe Storm ×3, Snowstorm |
| 2020s | 2 | Hurricane ×2 |
The last 10
Widest declarations that included Mercer County
- Remnants of Hurricane Ida (2021, DR-4614-NJ): 21 New Jersey counties designated.
- Remnants of Hurricane Ida (2021, EM-3573-NJ): 21 New Jersey counties designated.
- Hurricane Sandy (2012, DR-4086-NJ): 21 New Jersey counties designated.
Named storms in its declarations: Hurricane Ida (2021), Hurricane Sandy (2012), Tropical Storm Lee (2011), Hurricane Irene (2011), Hurricane Katrina (2005), Hurricane Floyd (1999).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. New Jersey also had 2 statewide declarations with no county list.
Tornado record since 1950 13
| Tornadoes touching the county | 13 |
|---|---|
| Strongest-rated | (E)F3 ×1 |
| Peak month | June (4) |
| Deadliest | 13 Jun 1958, F2, 0.1 mi path, 0 killed, 1 injured |
| Longest path | 24 Jun 1960, F3, 12.9 mi path |
| Most recent | 14 Jun 2024, EF0, 0.1 mi path |
| Deaths / injuries on those paths | 0 / 1 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 5 | 4 | 3 | 1 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 1 | 2 | 0 | 1 | 1 | 1 | 2 | 5 |
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 Mercer County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Mercer County (this page) | — | Relatively High | 95.4 | Strong wind |
| Middlesex County | 30 km | Relatively High | 97.8 | Strong wind |
| Somerset County | 32 km | Relatively Moderate | 90.9 | Inland flooding |
| Bucks County, PA | 35 km | Relatively High | 94.8 | Ice storm |
| Hunterdon County | 36 km | Relatively Low | 78.7 | Strong wind |
| Monmouth County | 40 km | Relatively High | 96.3 | Strong wind |
Nearest by distance between county centres. Every county in New Jersey, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Moderate 46.9 |
|---|---|
| Community resilience | Relatively High 70.2 |
| Community risk factor | 1.10 |
| Expected annual loss, all hazards | $176 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 Mercer County's main hazards
- Right now: National Weather Service alerts for New Jersey · all official warnings on Global Incident Tracker.
- Strong wind: Power outages now
- Winter weather: Power outages now · Carbon monoxide in winter
- 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 Mercer County
What natural disasters is Mercer County, New Jersey most at risk from?
Mercer County, New Jersey has a Relatively High natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 95.4 out of 100, higher than about 95% of US counties, with strong winds, winter storms and inland (river and flash) flooding scoring highest of its 18 hazards and $176 million a year in expected losses.
How many federal disaster declarations has Mercer County had?
OpenFEMA lists 26 federal disaster declarations that included Mercer County since 1965, not counting 2 for COVID-19; the latest is DR-4614-NJ (Remnants of Hurricane Ida, declared 5 September 2021). Another 2 New Jersey declarations were made statewide without a county list.
How many tornadoes have hit Mercer County?
NOAA's Storm Prediction Center recorded 13 tornadoes touching Mercer County from 1950 to 2025. The deadliest: 13 Jun 1958, F2, 0.1 mi path, 0 killed, 1 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.