Story County, Iowa Natural Disaster Risk
FEMA National Risk Index assessment · IA
LowComposite Risk Score
National percentile: 69th
Story County faces low composite natural disaster risk (NRI Risk Index score 68.8, 69th national percentile), driven primarily by drought and tornado exposure. Expected annual loss across all 18 hazard types is $36M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Story County is low, with a National Risk Index score of 68.8 out of 100 — placing it in the 69th national percentile and below the national average for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Risk here concentrates in drought (extended dry periods that stress water supplies and agriculture) at High risk — $4M in expected annual loss and about 6.44 events per year; tornado (violently rotating columns of air capable of catastrophic local damage) at High risk — $10M in expected annual loss and about 0.59 events per year; and winter weather (heavy snow, blizzards, and hazardous winter conditions) at High risk — $533K in expected annual loss and about 15.89 events per year. Across all hazards, FEMA estimates $36M in expected annual loss for a population of 99K.
Beyond physical exposure, Story 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 county's disaster history tells the same story: Story County has received 21 federal disaster declarations since 1969, including 12 for severe storm events and 6 for flood events. The most recent was Severe Storms, Tornadoes, and Flooding (severe storm), declared in May 2024.
Among 99 Iowa counties, Story County ranks #9 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Drought | High | 6.44 / yr | $4M |
| Tornado | High | 0.59 / yr | $10M |
| Winter Weather | High | 15.89 / yr | $533K |
| Hail | Medium | 6.20 / yr | $2M |
| Strong Wind | Medium | 6.05 / yr | $1M |
| Riverine Flood | Low | 2.68 / yr | $16M |
| Ice Storm | Medium | 0.68 / yr | $209K |
| Lightning | Low | 42.95 / yr | $380K |
| Landslide | Very Low | 0.07 / yr | $1K |
| Cold Wave | Low | 7.79 / yr | $692K |
| Earthquake | Very Low | 0.00 / yr | $142K |
| Wildfire | Very Low | 0.00 / yr | $19K |
| Hurricane | Very Low | 0.01 / yr | $5K |
| Heat Wave | Very Low | 5.37 / yr | $37K |
| 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
Story County has received 21 federal disaster declarations since 1969, most recently Severe Storms, Tornadoes, and Flooding in May 2024. Most frequent causes: Severe Storm (12), Flood (6), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| May 2024 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| August 2020 | Severe Storm | Severe Storms |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| August 2018 | Severe Storm | Severe Storms, Tornadoes, Straight-Line Winds, and Flooding |
| July 2013 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| August 2011 | Severe Storm | Severe Storms, Straight-Line Winds, and Flooding |
| July 2010 | Severe Storm | Severe Storms, Flooding, and Tornadoes |
| March 2010 | Severe Storm | Severe Winter Storm |
| May 2008 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
Showing the 10 most recent of 21 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Story County?
Story County has a composite FEMA National Risk Index score of 68.8 out of 100, placing it in the Low category and the 69th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Story County?
The three highest-rated hazards are Drought (High, $4M EAL), Tornado (High, $10M EAL), Winter Weather (High, $533K EAL). These account for most of the county's expected annual losses.
How does Story County compare to other Iowa counties?
Story County ranks #9 of 99 Iowa counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Story County had?
FEMA records 21 federal disaster declarations for Story County since 1969, most often 12 for severe storm events and 6 for flood 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. Story County's $36M EAL is a statistical average, not a guarantee for any specific year or address.