Rock County, Wisconsin Natural Disaster Risk
FEMA National Risk Index assessment · WI
MediumComposite Risk Score
National percentile: 86th
Rock County faces medium composite natural disaster risk (NRI Risk Index score 86.4, 86th national percentile), driven primarily by hail and tornado exposure. Expected annual loss across all 18 hazard types is $73M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Rock County at medium composite risk, with a National Risk Index score of 86.4 out of 100 — placing it in the 86th 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.
Risk here concentrates in hail (ice stones from severe thunderstorms that damage property and crops) at High risk — $4M in expected annual loss and about 4.34 events per year; tornado (violently rotating columns of air capable of catastrophic local damage) at High risk — $13M in expected annual loss and about 0.58 events per year; and cold wave (prolonged spells of dangerously low temperatures) at High risk — $13M in expected annual loss and about 5.37 events per year. Across all hazards, FEMA estimates $73M in expected annual loss for a population of 164K.
Beyond physical exposure, Rock 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: Rock County has received 16 federal disaster declarations since 1973, including 7 for severe storm events and 3 for flood events. The most recent was Severe Storms, Tornadoes, and Flooding (flood), declared in June 2026.
Among 72 Wisconsin counties, Rock County ranks #7 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Hail | High | 4.34 / yr | $4M |
| Tornado | High | 0.58 / yr | $13M |
| Cold Wave | High | 5.37 / yr | $13M |
| Riverine Flood | Medium | 2.11 / yr | $38M |
| Strong Wind | High | 5.46 / yr | $2M |
| Lightning | High | 38.50 / yr | $1M |
| Heat Wave | Medium | 3.63 / yr | $2M |
| Winter Weather | Medium | 14.05 / yr | $114K |
| Landslide | Very Low | 0.13 / yr | $3K |
| Earthquake | Very Low | 0.00 / yr | $529K |
| Ice Storm | Low | 0.63 / yr | $147K |
| Drought | Low | 6.60 / yr | $152K |
| Wildfire | Very Low | 0.00 / yr | $14K |
| Hurricane | Very Low | 0.01 / yr | $4K |
| 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
Rock County has received 16 federal disaster declarations since 1973, most recently Severe Storms, Tornadoes, and Flooding in June 2026. Most frequent causes: Severe Storm (7), Flood (3), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| June 2026 | Flood | Severe Storms, Tornadoes, and Flooding |
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| June 2008 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| March 2008 | Snowstorm | Record Snow and Near Record Snow |
| August 2007 | Severe Storm | Severe Storms and Flooding |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| June 2004 | Severe Storm | Severe Storms and Flooding |
| January 2001 | Snowstorm | Snow |
| August 1998 | Severe Storm | Severe Storms and Flooding |
Showing the 10 most recent of 16 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Rock County?
Rock County has a composite FEMA National Risk Index score of 86.4 out of 100, placing it in the Medium category and the 86th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Rock County?
The three highest-rated hazards are Hail (High, $4M EAL), Tornado (High, $13M EAL), Cold Wave (High, $13M EAL). These account for most of the county's expected annual losses.
How does Rock County compare to other Wisconsin counties?
Rock County ranks #7 of 72 Wisconsin counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Rock County had?
FEMA records 16 federal disaster declarations for Rock County since 1973, most often 7 for severe storm events and 3 for flood events. The most recent was Severe Storms, Tornadoes, and Flooding, declared in June 2026.
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. Rock County's $73M EAL is a statistical average, not a guarantee for any specific year or address.