Mercer County, New Jersey Natural Disaster Risk
FEMA National Risk Index assessment · NJ
HighComposite Risk Score
National percentile: 95th
Mercer County faces high composite natural disaster risk (NRI Risk Index score 95.4, 95th national percentile), driven primarily by strong wind and winter weather exposure. Expected annual loss across all 18 hazard types is $176M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Mercer County at high composite risk, with a National Risk Index score of 95.4 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.
Risk here concentrates in strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at Very High risk — $13M in expected annual loss and about 7.02 events per year; winter weather (heavy snow, blizzards, and hazardous winter conditions) at Very High risk — $1M in expected annual loss and about 10.64 events per year; and riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at High risk — $114M in expected annual loss and about 3.64 events per year. Across all hazards, FEMA estimates $176M in expected annual loss for a population of 386K.
Beyond physical exposure, Mercer County has a medium 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.
The county's disaster history tells the same story: Mercer County has received 28 federal disaster declarations since 1965, including 9 for hurricane events and 7 for severe storm events. The most recent was Remnants of Hurricane Ida (hurricane), declared in September 2021.
Among 21 New Jersey counties, Mercer County ranks #9 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Strong Wind | Very High | 7.02 / yr | $13M |
| Winter Weather | Very High | 10.64 / yr | $1M |
| Riverine Flood | High | 3.64 / yr | $114M |
| Ice Storm | Very High | 1.09 / yr | $2M |
| Heat Wave | Medium | 10.96 / yr | $7M |
| Hurricane | High | 0.11 / yr | $18M |
| Earthquake | Medium | 0.00 / yr | $11M |
| Lightning | High | 33.63 / yr | $1M |
| Cold Wave | Medium | 0.84 / yr | $5M |
| Tornado | Medium | 0.09 / yr | $4M |
| Wildfire | Low | 0.00 / yr | $216K |
| Drought | Low | 3.22 / yr | $305K |
| Coastal Flood | Low | 6.17 / yr | $329K |
| Landslide | Very Low | 0.07 / yr | $2K |
| Hail | Very Low | 2.40 / yr | $110K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Mercer County has received 28 federal disaster declarations since 1965, most recently Remnants of Hurricane Ida in September 2021. Most frequent causes: Hurricane (9), Severe Storm (7), Snowstorm (4).
| Declared | Type | Disaster |
|---|---|---|
| September 2021 | Hurricane | Remnants of Hurricane Ida |
| September 2021 | Hurricane | Remnants of Hurricane Ida |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| March 2016 | Severe Storm | Severe Winter Storm and Snowstorm |
| October 2012 | Hurricane | Hurricane Sandy |
| October 2012 | Hurricane | Hurricane Sandy |
| October 2011 | Severe Storm | Remnants of Tropical Storm Lee |
| August 2011 | Hurricane | Hurricane Irene |
| August 2011 | Hurricane | Hurricane Irene |
Showing the 10 most recent of 28 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Mercer County?
Mercer County has a composite FEMA National Risk Index score of 95.4 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 Mercer County?
The three highest-rated hazards are Strong Wind (Very High, $13M EAL), Winter Weather (Very High, $1M EAL), Riverine Flood (High, $114M EAL). These account for most of the county's expected annual losses.
How does Mercer County compare to other New Jersey counties?
Mercer County ranks #9 of 21 New Jersey counties for overall natural disaster risk, with a high rating.
How many federally declared disasters has Mercer County had?
FEMA records 28 federal disaster declarations for Mercer County since 1965, most often 9 for hurricane events and 7 for severe storm events. The most recent was Remnants of Hurricane Ida, declared in September 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. Mercer County's $176M EAL is a statistical average, not a guarantee for any specific year or address.