Polk County, Iowa Natural Disaster Risk
FEMA National Risk Index assessment · IA
MediumComposite Risk Score
National percentile: 92th
Polk County faces medium composite natural disaster risk (NRI Risk Index score 92.0, 92th national percentile), driven primarily by strong wind and tornado exposure. Expected annual loss across all 18 hazard types is $138M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Polk County at medium composite risk, with a National Risk Index score of 92.0 out of 100 — placing it in the 92nd national percentile and near the national midpoint for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of Polk County's expected losses come from strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at Very High risk — $11M in expected annual loss and about 6.01 events per year; tornado (violently rotating columns of air capable of catastrophic local damage) at High risk — $31M in expected annual loss and about 0.59 events per year; and hail (ice stones from severe thunderstorms that damage property and crops) at High risk — $7M in expected annual loss and about 6.13 events per year. Across all hazards, FEMA estimates $138M in expected annual loss for a population of 492K.
Beyond physical exposure, Polk County has a very low social vulnerability rating (how susceptible the population is to harm) and a very 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 federal record bears this out: Polk County has received 20 federal disaster declarations since 1965, including 8 for flood events and 7 for severe storm events. The most recent was Severe Storms, Tornadoes, and Flooding (severe storm), declared in May 2024.
Among 99 Iowa counties, Polk County ranks #1 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Strong Wind | Very High | 6.01 / yr | $11M |
| Tornado | High | 0.59 / yr | $31M |
| Hail | High | 6.13 / yr | $7M |
| Heat Wave | High | 7.32 / yr | $11M |
| Drought | High | 6.46 / yr | $3M |
| Riverine Flood | Medium | 5.07 / yr | $61M |
| Ice Storm | High | 0.93 / yr | $1M |
| Cold Wave | High | 6.00 / yr | $10M |
| Winter Weather | High | 14.11 / yr | $506K |
| Lightning | Medium | 44.35 / yr | $816K |
| Landslide | Low | 0.12 / yr | $6K |
| Earthquake | Low | 0.00 / yr | $820K |
| Wildfire | Very Low | 0.00 / yr | $91K |
| Hurricane | Very Low | 0.01 / yr | $14K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Polk County has received 20 federal disaster declarations since 1965, most recently Severe Storms, Tornadoes, and Flooding in May 2024. Most frequent causes: Flood (8), Severe Storm (7), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| May 2024 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| May 2024 | Tornado | Severe Storms and Tornadoes |
| August 2020 | Severe Storm | Severe Storms |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| March 2019 | Flood | Severe Storms and Flooding |
| August 2018 | Severe Storm | Severe Storms, Tornadoes, Straight-Line Winds, and Flooding |
| July 2010 | Severe Storm | Severe Storms, Flooding, and Tornadoes |
| May 2008 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| March 2007 | Severe Storm | Severe Winter Storms |
Showing the 10 most recent of 20 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Polk County?
Polk County has a composite FEMA National Risk Index score of 92.0 out of 100, placing it in the Medium category and the 92th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Polk County?
The three highest-rated hazards are Strong Wind (Very High, $11M EAL), Tornado (High, $31M EAL), Hail (High, $7M EAL). These account for most of the county's expected annual losses.
How does Polk County compare to other Iowa counties?
Polk County ranks #1 of 99 Iowa counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Polk County had?
FEMA records 20 federal disaster declarations for Polk County since 1965, most often 8 for flood events and 7 for severe storm events. The most recent was Severe Storms, Tornadoes, and Flooding, declared in May 2024.
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. Polk County's $138M EAL is a statistical average, not a guarantee for any specific year or address.