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

Sioux County Disaster Risk

Sioux County, Iowa

FEMA Risk Rating

Relatively Low

National Percentile

52th

of 3,144 counties

State Rank

#23

of 99 (1 = highest risk)

Flood Risk

49th

percentile

Hazard Risk Breakdown

Flood

River, coastal, and surface flooding risk

Relatively Low

Higher than 49% of US counties

Wildfire

Wildland and wildland-urban interface fire risk

Very Low

Higher than 40% of US counties

Tornado

Tornado and severe thunderstorm risk

Relatively Low

Higher than 79% of US counties

Earthquake

Seismic activity and ground shaking risk

Very Low

Higher than 19% of US counties

Risk Overview

About Natural Disaster Risk in Sioux County, Iowa

Sioux County's risk approaches national average

Sioux County's composite risk score of 52.39 with a Relatively Low rating sits modestly above the national average. While not alarming, it signals moderate exposure to natural hazards across multiple categories.

Sioux ranks in Iowa's middle tier

At 52.39, Sioux County exceeds Iowa's state average of 39.68, placing it in the middle-to-upper range of the state's risk profile. Several Iowa counties pose lower risks, while others face considerably steeper hazards.

Sioux ranks higher than adjacent counties

Sioux County's 52.39 score exceeds neighboring Sac County (27.29) and approaches Story County (68.83). It represents a moderate risk level for northwestern Iowa.

Tornadoes and floods demand attention

Tornado risk (79.36) and flood risk (49.46) drive Sioux County's hazard profile, with wildfire (39.66) presenting a secondary concern. The combination of strong wind and water threats requires active preparedness.

Ensure flood and wind coverage

Sioux County residents should verify their homeowner's policies include tornado and wind protection, and consider flood insurance given the moderate flood risk. Review your policy limits and update coverage after major home improvements.

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

Preparedness Guide

What to Prepare for in Sioux County

Top Hazards by Exposure

  1. #1
    TornadoPrepare
    79th percentile
  2. #2
    FloodPrepare
    49th percentile
  3. #3
    WildfirePrepare
    40th percentile

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

Risk Advisory: Sioux County

Risk Verdict

With a national percentile rank of 52th, Sioux County faces below-average hazard exposure relative to U.S. counties as a whole. Above-average risk does not mean imminent danger; it signals that informed, hazard-specific preparedness has high value here.

Hazard Breakdown

Tornado risk is Sioux County's dominant natural hazard, ranked at the 79th percentile nationally under FEMA's National Risk Index. Flood ranks second at the 49th percentile nationally. Additional tracked hazards include wildfire (40th percentile), earthquake (19th percentile).

Preparedness Context

At the 79th percentile nationally for tornado risk, Sioux County households benefit most from a reliable alert system — a NOAA weather radio that activates during overnight hours when residents may not be checking smartphone alerts. The secondary flood hazard at the 49th percentile nationally adds seasonal complexity to Sioux County's preparedness calendar, since flood and tornado risk often peak at different points in the year. For Sioux County households, a pre-decided family shelter plan — who goes where, how children are retrieved from school during a warning, and a neighborhood meet-up point if phones fail — provides real protection that no supply kit alone can replicate.

Regional Context

At 12.7 points above the Iowa state average, Sioux County carries meaningfully higher natural disaster exposure than a typical Iowa county.

Is your household prepared for Sioux 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 Sioux County, IA?
Sioux County has a FEMA National Risk Index rating of Relatively Low, placing it in the 52th 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 Sioux County?
Sioux County is evaluated for five major natural hazard types: tornado (79th percentile), flooding (49th percentile), wildfire (40th percentile), earthquake (19th percentile). The highest-risk hazard is tornado at the 79th 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 Sioux County risk compare to the Iowa average?
Sioux County's composite risk percentile is 52th, compared to the Iowa state average of 40th percentile. The state's overall risk rating is Very Low. This means Sioux County faces higher natural disaster risk than the typical county in Iowa.
Is Sioux County at risk for tornado?
Yes, Sioux County's tornado risk is at the 79th percentile nationally. This places it in the top quartile for this hazard type. For flooding specifically, Sioux County is at the 49th 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 Sioux County higher risk than average?
Sioux County's composite risk score of 52th percentile is above the Iowa state average of 40th percentile. This elevated risk is driven by tornado exposure (79th percentile). Geographic location, terrain, climate patterns, and proximity to flood zones or fault lines all influence a county's risk profile.
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.