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FEMA NRI 1.19.0Updated Nov 2023 · Coverage 2014–2023Methodology

Johnson County Disaster Risk

Johnson County, Iowa

FEMA Risk Rating

Relatively Moderate

National Percentile

87th

of 3,144 counties

State Rank

#2

of 99 (1 = highest risk)

Flood Risk

80th

percentile

Hazard Risk Breakdown

Flood

River, coastal, and surface flooding risk

Relatively Low

Higher than 80% of US counties

Wildfire

Wildland and wildland-urban interface fire risk

Relatively Low

Higher than 64% of US counties

Tornado

Tornado and severe thunderstorm risk

Relatively High

Higher than 98% of US counties

Earthquake

Seismic activity and ground shaking risk

Relatively Low

Higher than 45% of US counties

Hurricane

Tropical cyclone and hurricane risk

Very Low

Higher than 14% of US counties

Risk Overview

About Natural Disaster Risk in Johnson County, Iowa

Johnson County faces elevated disaster risk

Johnson County's composite risk score of 87.44 nearly doubles the national average of 39.68, earning a relatively moderate risk rating. The county experiences significantly higher natural hazard exposure than most American counties, particularly for tornadoes and flooding.

Highest-risk county in Iowa by far

Johnson County scores 87.44, far exceeding Iowa's state average of 39.68 and ranking as the riskiest county statewide. The county's tornado risk of 98.19 and flood risk of 79.77 represent the most severe exposure in the state.

Dramatically higher risk than adjacent areas

Johnson County's score of 87.44 vastly exceeds neighboring Jackson County (36.07), Jasper County (43.67), and Jones County (32.67). The county faces nearly double the composite risk of surrounding areas, reflecting exceptional hazard concentration.

Tornadoes and flooding pose major threats

Johnson County residents face tornado risk of 98.19—the highest in the state—and flood risk of 79.77, both substantially above state averages. Spring tornado seasons and seasonal flooding represent the most serious natural disaster threats residents encounter.

Comprehensive coverage essential for Johnson County

With tornado risk at 98.19 and flood risk at 79.77, homeowners must secure both comprehensive storm coverage and separate flood insurance. Invest in home hardening measures like reinforced safe rooms and ensure your policies include full wind, hail, and water damage protection.

Source: FEMA National Risk Index · Narrative reviewed by Evan Brooks, Data Editor

Preparedness Guide

What to Prepare for in Johnson County

Top Hazards by Exposure

  1. #1
    TornadoPrepare
    98th percentile
  2. #2
    FloodPrepare
    80th percentile
  3. #3
    WildfirePrepare
    64th percentile

Source: FEMA National Risk Index v1.19.0 · Percentiles are national (3,144 counties)

Local Resources

Risk Advisory: Johnson County

Risk Verdict

Johnson County faces a moderate natural disaster risk profile, ranking at the 87th percentile nationally under FEMA's composite risk model. This risk level calls for more than general awareness: insurance coverage review, a family communication plan, and a prepared go-bag are practical priorities.

Hazard Breakdown

Tornado risk is Johnson County's dominant natural hazard, ranked at the 98th percentile nationally under FEMA's National Risk Index. Flood ranks second at the 80th percentile nationally. Additional tracked hazards include wildfire (64th percentile), earthquake (45th percentile), hurricane (14th percentile).

Preparedness Context

Tornado risk is Johnson County's top-ranked natural hazard at the 98th percentile nationally. For Johnson County households, the most protective action available is identifying a reinforced interior room on the lowest floor — a bathroom, closet, or central hallway away from windows. Flood is the second hazard driver for Johnson County at the 80th percentile nationally, meaning households should maintain awareness of both severe-weather and flood-specific warning systems. A battery-powered NOAA All Hazards weather radio with an auto-alert tone is the highest-leverage single item for tornado preparedness in Johnson County, since it delivers warnings even when power is out and phone networks are congested.

Regional Context

Johnson County's composite risk score sits 47.8 points above the Iowa county average, placing it among the more hazard-exposed counties in the state.

Is your household prepared for Johnson County's hazards?

Review FEMA's county-specific preparedness checklists and emergency planning guides.

FEMA Ready Guide →

Frequently Asked Questions

What is the natural disaster risk in Johnson County, IA?
Johnson County has a FEMA National Risk Index rating of Relatively Moderate, placing it in the 87th percentile nationally out of 3,144 counties. This composite score reflects the county's overall exposure to natural hazards including floods, wildfires, tornadoes, earthquakes, and hurricanes, weighted by expected annual loss and social vulnerability.
What types of natural hazards affect Johnson County?
Johnson County is evaluated for five major natural hazard types: tornado (98th percentile), flooding (80th percentile), wildfire (64th percentile), earthquake (45th percentile), hurricane (14th percentile). The highest-risk hazard is tornado at the 98th percentile nationally. These scores are derived from FEMA's National Risk Index, which analyzes expected annual loss, social vulnerability, and community resilience for each hazard type.
How does Johnson County risk compare to the Iowa average?
Johnson County's composite risk percentile is 87th, compared to the Iowa state average of 40th percentile. The state's overall risk rating is Very Low. This means Johnson County faces higher natural disaster risk than the typical county in Iowa.
Is Johnson County at risk for tornado?
Yes, Johnson County's tornado risk is at the 98th percentile nationally. This places it in the top quartile for this hazard type. For flooding specifically, Johnson County is at the 80th percentile.
How is natural disaster risk measured?
FEMA's National Risk Index (NRI) calculates risk scores for 18 natural hazard types across all U.S. counties and census tracts. The composite score combines Expected Annual Loss (estimated dollar losses from each hazard), Social Vulnerability (demographic factors affecting disaster impact), and Community Resilience (ability to recover). Percentile scores rank each county against all 3,144 U.S. counties, and risk ratings range from Very Low to Very High.
Why is Johnson County higher risk than average?
Johnson County's composite risk score of 87th percentile is above the Iowa state average of 40th percentile. This elevated risk is driven by tornado exposure (98th percentile), along with flooding and wildfire risk. Geographic location, terrain, climate patterns, and proximity to flood zones or fault lines all influence a county's risk profile.

Counties with Similar Risk

Linn County

Iowa

-0.7

Relatively Moderate

87th percentile

Scott County

Iowa

-2.5

Relatively Moderate

85th percentile

Woodbury County

Iowa

-4.2

Relatively Moderate

83th percentile

By Evan Brooks, Data EditorUpdated Reviewed by Evan Brooks, Data Editor

Data Source

Risk data sourced from the FEMA National Risk Index (NRI). Risk scores are relative rankings (0–100) across all US counties — not absolute risk measures. Higher scores indicate higher relative risk compared to other counties.

Disclaimer: This data is informational only. It is not financial, insurance, or legal advice. Always consult a qualified professional before making insurance or real estate decisions.

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