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Natural hazard risk in Mercer County, New Jersey

Updated October 30, 2026. Based on FEMA, NOAA and OpenFEMA data. Published by Humblebee.

FEMA overall Risk Index rating: Relatively High (score 95.3 of 100)[5]

Expected annual loss (FEMA)
$176.2 million[1]
Federal disaster declarations since 1965
25[2]
NFIP flood claims paid, 1978 to 2026
$48.4 million[3]
Tornadoes recorded, 1950 to 2024
13[4]

FEMA's National Risk Index rates overall natural hazard risk for Mercer County as Relatively High, with a score of 95.3 out of 100[5]. The hazards with the highest FEMA scores in this county are strong wind, winter weather and inland flooding[6].

FEMA risk ratings for each hazard

Ratings and expected losses from the FEMA National Risk Index. Each rating compares this county with all US counties for that hazard, from Very Low to Very High. They are planning estimates, not predictions, and they do not describe any single property.

FEMA's National Risk Index (version 1.20, December 2025) rates Mercer County Relatively High overall, with a score of 95.3 that compares the county with all US counties[5]. FEMA estimates Expected Annual Loss from all 18 natural hazards at $176.2 million a year[1]. FEMA's hazard-type values list inland flooding ($113.6 million a year), hurricane ($18.1 million a year) and strong wind ($12.7 million a year), in that order[7]. Expected Annual Loss is an estimate of average yearly loss, and FEMA says the index does not predict damage in the next year[8]. FEMA rates Social Vulnerability Relatively Moderate, which describes how susceptible social groups are to harm from natural hazards[9]. FEMA rates Community Resilience Relatively High, which describes a community's ability to prepare for, withstand and recover from hazards[10].

Hazards sorted by FEMA hazard-type Risk Index score, highest first
HazardFEMA risk ratingExpected annual loss
Strong WindVery High$12.7 million[11]
Winter WeatherVery High$1.1 million[12]
Inland FloodingRelatively High$113.6 million[13]
Ice StormVery High$1.9 million[14]
Heat WaveRelatively Moderate$6.8 million[15]
HurricaneRelatively High$18.1 million[16]
EarthquakeRelatively Moderate$10.6 million[17]
LightningRelatively High$1.5 million[18]
Cold WaveRelatively Moderate$4.8 million[19]
TornadoRelatively Moderate$4.1 million[20]
WildfireRelatively Low$216,000[21]
DroughtRelatively Low$305,000[22]
Coastal FloodingRelatively Low$329,000[23]
LandslideVery Low$1,608[24]
HailVery Low$110,000[25]

Rated Not Applicable by FEMA for this county: avalanche, tsunami, volcanic activity[26].

Social vulnerability and community resilience

FEMA uses these two ratings to scale expected losses into the Risk Index.

FEMA measureRatingScore
Social vulnerabilityRelatively Moderate46.8[9]
Community resilienceRelatively High70.2[10]

Flooding and flood insurance

FEMA rates inland flooding risk Relatively High compared with other US counties, with an Expected Annual Loss of $113.6 million a year[13]. FEMA rates coastal flooding Relatively Low[23]. OpenFEMA lists 1,294 residential flood insurance contracts in force, a penetration rate of 1.2% as of 2026-08-03[27]. The same data shows 41.7% of homes inside the mapped Special Flood Hazard Area are insured[27]. OpenFEMA data tallied by HazardFacts shows 2,432 NFIP claims for losses from 1978 to 2026, and NFIP paid $48.4 million in total[3]. For a specific address, check FEMA's Flood Map Service Center[28].

Measure Value
Inland Flooding, FEMA risk rating[13] Relatively High, $113.6 million expected loss a year
Coastal Flooding, FEMA risk rating[23] Relatively Low, $329,000 expected loss a year
NFIP residential flood policies in force (2026)[27] 1,294 of 107,040 homes
Homes in FEMA's mapped high-risk flood area (SFHA)[27] 1,826, of which 761 insured
NFIP flood claims, 1978 to 2026[3] 2,432 filed, $48.4 million paid

Is a specific address in a flood zone? Only FEMA's flood maps answer that, property by property[28]. This page describes the whole county.

Search an address on the FEMA Flood Map Service Center

Disaster declarations and tornado records

OpenFEMA lists 25 federal disaster declarations for natural hazards that include Mercer County since 1965[2]. By incident type, hurricane has 9 and severe storm has 7[2]. The most recent are two declarations for the remnants of Hurricane Ida in 2021[29]. NOAA's tornado database records 13 tornadoes touching the county from 1950 to 2024, and the most recent was on 2024-06-14[4].

Federal disaster declarations for natural hazards that include Mercer County, since 1965
Incident type Declarations
Hurricane[2] 9
Severe Storm[2] 7
Snowstorm[2] 4
Drought[2] 2
Flood[2] 2
Fire[2] 1
Most recent declarations
Declaration Incident Declared
DR-4614-NJ[29] Remnants Of Hurricane Ida 2021-09-05
EM-3573-NJ[29] Remnants Of Hurricane Ida 2021-09-02
DR-4264-NJ[29] Severe Winter Storm And Snowstorm 2016-03-14
DR-4086-NJ[29] Hurricane Sandy 2012-10-30
EM-3354-NJ[29] Hurricane Sandy 2012-10-28

How to prepare

Steps from Ready.gov, FEMA's preparedness site, for the hazards with the highest FEMA ratings here. Follow instructions from local officials and the National Weather Service when a warning is issued.

Winter storms and cold

Before

  • Insulate your home and learn how to keep pipes from freezing.
  • Install and test smoke and carbon monoxide detectors with battery backup.
  • Keep several days of supplies in case the power goes out, including medication and pet needs.
  • Put an emergency kit in your car with jumper cables, sand, blankets, water and snacks, and keep the tank full.

During

  • Under a winter storm warning, find shelter right away.
  • Stay off the roads if you can. If you are stuck in your car, stay inside it.
  • Run generators and grills only outdoors, away from windows, and never heat your home with an oven or stove.

Source: Ready.gov, winter storms and cold

Floods

Before

  • Check your flood risk with FEMA's Flood Map Service Center, and remember that floods do not follow map lines.
  • Sign up for your community's warning system. NOAA Weather Radio also broadcasts alerts.
  • Buy flood insurance through the NFIP well before a disaster. Homeowners policies do not cover flooding, and a new policy typically takes up to 30 days to go into effect.
  • Make a household plan with evacuation routes, shelter locations and what to do in a flash flood.
  • Keep important documents in a waterproof container and make password-protected digital copies.

During

  • If you are told to evacuate, leave right away and never drive around barricades.
  • Do not walk, swim or drive through floodwater. Six inches of moving water can knock you down.
  • If you are trapped in a building, go to the highest level, but do not climb into a closed attic.

Source: Ready.gov, floods

Extreme heat

Before

  • Learn the signs of heat illness and how to respond.
  • Do not rely on a fan as your main way to stay cool. Fans do not lower body temperature.
  • Find cool public places, such as libraries or malls, or ask your local health department.
  • Keep heat out with window shades, weather stripping and insulation.
  • If you cannot afford cooling costs, contact LIHEAP for help.

During

  • Never leave a person or an animal in a parked car in warm weather.
  • If your home has no air conditioning, go to a cooling center.
  • Wear light, loose clothing, drink plenty of fluids and avoid hard outdoor work in the middle of the day.

Source: Ready.gov, extreme heat

Questions people ask

Is Mercer County, NJ at risk of flooding?
FEMA rates inland flooding risk Relatively High for Mercer County compared with other US counties[13]. FEMA rates coastal flooding Relatively Low[23].
How do I check the flood zone for an address in Mercer County?
County ratings do not show the flood zone of a single address. Look up the address in FEMA's Flood Map Service Center or ask the local floodplain manager[28].
Does Mercer County get tornadoes?
NOAA's tornado database records 13 tornadoes touching Mercer County from 1950 to 2024[4]. FEMA rates tornado risk Relatively Moderate compared with other US counties[20].
How many federal disasters were declared in Mercer County?
OpenFEMA lists 25 federal disaster declarations for natural hazards that include Mercer County since 1965[2].
Is Mercer County at risk of earthquakes?
FEMA rates earthquake risk Relatively Moderate for Mercer County compared with other US counties[17].

Facts and sources

  1. FEMA National Risk Index (version 1.20, December 2025): Expected Annual Loss from all 18 natural hazards in Mercer County is $176.2 million a year (Expected Annual Loss rating Relatively Moderate, score 95.1). Of this, buildings account for $146.5 million, injuries and deaths (converted to dollars by FEMA) for... FEMA National Risk Index
  2. OpenFEMA Disaster Declarations Summaries list 25 federal disaster declarations for natural hazards that include Mercer County since 1965 (16 major disaster, 9 emergency or fire management). By incident type: hurricane 9, severe storm 7, snowstorm 4, drought 2, flood 2, fire 1. Biological (such as COVID-19) and... OpenFEMA Disaster Declarations
  3. HazardFacts tally of OpenFEMA NFIP Redacted Claims (losses from 1978 to 2026): 2,432 National Flood Insurance Program claims were filed for losses in Mercer County, 1,879 of them with a payment, and NFIP paid $48.4 million in total (building, contents and increased cost of compliance, in dollars of the year paid).... OpenFEMA NFIP claims
  4. NOAA Storm Prediction Center tornado database (1950 to 2024): 13 recorded tornadoes touched Mercer County. The strongest were rated F3 (most recent of them on 1960-06-24). 1 were rated F3/EF3 or stronger. The most recent recorded tornado was on 2024-06-14. Ratings used the Fujita scale until early 2007 and the... NOAA Storm Prediction Center
  5. FEMA National Risk Index (version 1.20, December 2025): the overall natural hazard Risk Index rating for Mercer County is Relatively High, with a Risk Index score of 95.3 out of 100. The score is the county's percentile rank among all US counties. FEMA National Risk Index
  6. Among the 18 hazards in the FEMA National Risk Index (version 1.20, December 2025), the hazards with the highest hazard-type Risk Index scores for Mercer County are strong wind (99.5, Very High), winter weather (97.7, Very High), inland flooding (97.1, Relatively High). HazardFacts sorted FEMA's published scores;... FEMA National Risk Index
  7. HazardFacts sorted FEMA's hazard-type Expected Annual Loss values for Mercer County (National Risk Index v1.20): the largest are inland flooding ($113.6 million a year), hurricane ($18.1 million a year), strong wind ($12.7 million a year), out of $176.2 million a year from all 18 hazards. FEMA National Risk Index
  8. FEMA's National Risk Index FAQ (December 2025): Expected Annual Loss is FEMA's estimate of the average economic loss in dollars from natural hazards each year. The index is not meant to predict how much damage a community will have in the next year, and a hazard can still cause damage where a rating is low. Scores... FEMA National Risk Index documentation
  9. FEMA National Risk Index (version 1.20, December 2025): Social Vulnerability rating for Mercer County is Relatively Moderate (score 46.8). FEMA describes social vulnerability as how susceptible social groups are to the harm natural hazards cause. FEMA National Risk Index
  10. FEMA National Risk Index (version 1.20, December 2025): Community Resilience rating for Mercer County is Relatively High (score 70.2). FEMA describes community resilience as a community's ability to prepare for, withstand and recover from hazards. FEMA National Risk Index
  11. FEMA National Risk Index (version 1.20, December 2025), strong wind in Mercer County: Risk Index rating Very High (score 99.5 of 100). Expected Annual Loss $12.7 million a year (rating Very High). Annualized frequency 7.02 events per year, from recorded occurrences over a period of record of 38 years. FEMA National Risk Index
  12. FEMA National Risk Index (version 1.20, December 2025), winter weather in Mercer County: Risk Index rating Very High (score 97.7 of 100). Expected Annual Loss $1.1 million a year (rating Very High). Annualized frequency 10.64 events per year, from recorded occurrences over a period of record of 18 years. FEMA National Risk Index
  13. FEMA National Risk Index (version 1.20, December 2025), inland flooding in Mercer County: Risk Index rating Relatively High (score 97.1 of 100). Expected Annual Loss $113.6 million a year (rating Relatively High). Annualized frequency 3.64 event-days per year, from recorded occurrences over a period of record of 26... FEMA National Risk Index
  14. FEMA National Risk Index (version 1.20, December 2025), ice storm in Mercer County: Risk Index rating Very High (score 96.3 of 100). Expected Annual Loss $1.9 million a year (rating Very High). Annualized frequency 1.09 event-days per year, from recorded occurrences over a period of record of 68 years. FEMA National Risk Index
  15. FEMA National Risk Index (version 1.20, December 2025), heat wave in Mercer County: Risk Index rating Relatively Moderate (score 95.7 of 100). Expected Annual Loss $6.8 million a year (rating Relatively Moderate). Annualized frequency 10.96 event-days per year, from recorded occurrences over a period of record of... FEMA National Risk Index
  16. FEMA National Risk Index (version 1.20, December 2025), hurricane in Mercer County: Risk Index rating Relatively High (score 94.6 of 100). Expected Annual Loss $18.1 million a year (rating Relatively High). Annualized frequency 0.11 events per year, from recorded occurrences over a period of record of 172 years for... FEMA National Risk Index
  17. FEMA National Risk Index (version 1.20, December 2025), earthquake in Mercer County: Risk Index rating Relatively Moderate (score 94.0 of 100). Expected Annual Loss $10.6 million a year (rating Relatively Moderate). FEMA's modeled annual frequency is 0.0019 events per year. FEMA National Risk Index
  18. FEMA National Risk Index (version 1.20, December 2025), lightning in Mercer County: Risk Index rating Relatively High (score 93.5 of 100). Expected Annual Loss $1.5 million a year (rating Relatively High). Annualized frequency 33.63 events per year, from recorded occurrences over a period of record of 24 years. FEMA National Risk Index
  19. FEMA National Risk Index (version 1.20, December 2025), cold wave in Mercer County: Risk Index rating Relatively Moderate (score 85.1 of 100). Expected Annual Loss $4.8 million a year (rating Relatively High). Annualized frequency 0.84 event-days per year, from recorded occurrences over a period of record of 18 years. FEMA National Risk Index
  20. FEMA National Risk Index (version 1.20, December 2025), tornado in Mercer County: Risk Index rating Relatively Moderate (score 81.9 of 100). Expected Annual Loss $4.1 million a year (rating Relatively Moderate). Annualized frequency 0.09 events per year, from recorded occurrences over a period of record of 38 years. FEMA National Risk Index
  21. FEMA National Risk Index (version 1.20, December 2025), wildfire in Mercer County: Risk Index rating Relatively Low (score 73.4 of 100). Expected Annual Loss $216,000 a year (rating Relatively Low). FEMA's modeled annual frequency is 0.0005 events per year. FEMA National Risk Index
  22. FEMA National Risk Index (version 1.20, December 2025), drought in Mercer County: Risk Index rating Relatively Low (score 62.0 of 100). Expected Annual Loss $305,000 a year (rating Relatively Low). Annualized frequency 3.22 event-days per year, from recorded occurrences over a period of record of 22 years. FEMA National Risk Index
  23. FEMA National Risk Index (version 1.20, December 2025), coastal flooding in Mercer County: Risk Index rating Relatively Low (score 56.8 of 100). Expected Annual Loss $329,000 a year (rating Relatively Low). FEMA's modeled annual frequency is 6.1712 events per year. FEMA National Risk Index
  24. FEMA National Risk Index (version 1.20, December 2025), landslide in Mercer County: Risk Index rating Very Low (score 53.4 of 100). Expected Annual Loss $1,608 a year (rating Very Low). FEMA National Risk Index
  25. FEMA National Risk Index (version 1.20, December 2025), hail in Mercer County: Risk Index rating Very Low (score 29.5 of 100). Expected Annual Loss $110,000 a year (rating Very Low). Annualized frequency 2.4 events per year, from recorded occurrences over a period of record of 37 years. FEMA National Risk Index
  26. FEMA National Risk Index (version 1.20, December 2025) rates these hazards Not Applicable for Mercer County: avalanche, tsunami, volcanic activity. FEMA uses Not Applicable when its source data has no historical record of the hazard in the community and the hazard is not considered geographically possible there. FEMA National Risk Index documentation
  27. NFIP Residential Penetration Rates (OpenFEMA, as of 2026-08-03): 1,294 residential flood insurance contracts were in force in Mercer County, out of 107,040 residential structures, a penetration rate of 1.2%. Inside FEMA's mapped Special Flood Hazard Area there were 1,826 residential structures and 761 contracts, a... OpenFEMA NFIP penetration rates
  28. FEMA's Flood Map Service Center is the official public source for flood maps (Flood Insurance Rate Maps) produced under the National Flood Insurance Program. Flood zones apply to specific properties: look up an address there or ask the local floodplain manager. County-level ratings do not tell you the flood zone of... FEMA Flood Map Service Center
  29. Most recent federal disaster declarations for natural hazards (table on this page). OpenFEMA Disaster Declarations

FEMA's National Risk Index compares each county with all other US counties. Ratings are relative (Very Low to Very High), not a measure of safety. Never call a place safe, unsafe, good or bad to live in. Risk Index and Expected Annual Loss values are FEMA estimates for planning. They do not predict next year's losses and do not apply to a single property. Flood zones are set by FEMA flood maps for specific properties. County ratings and flood insurance counts do not tell anyone whether an address is in a flood zone. Disaster declaration, NFIP and tornado counts are records of the past for this county only. Do not compare with other counties unless a fact does.

Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties, v1.20 (December 2025). Retrieved from fema.maps.arcgis.com on October 30, 2026. 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). This product uses the FEMA OpenFEMA API, but is not endorsed by FEMA.