Waukesha County, Wisconsin Natural Disaster Risk
FEMA National Risk Index assessment · WI
MediumComposite Risk Score
National percentile: 89th
Waukesha County faces medium composite natural disaster risk (NRI Risk Index score 88.9, 89th national percentile), driven primarily by cold wave and hail exposure. Expected annual loss across all 18 hazard types is $138M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Waukesha County is medium, with a National Risk Index score of 88.9 out of 100 — placing it in the 89th 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 Waukesha County's expected losses come from cold wave (prolonged spells of dangerously low temperatures) at High risk — $30M in expected annual loss and about 5.32 events per year; hail (ice stones from severe thunderstorms that damage property and crops) at High risk — $6M in expected annual loss and about 3.68 events per year; and tornado (violently rotating columns of air capable of catastrophic local damage) at High risk — $24M in expected annual loss and about 0.37 events per year. Across all hazards, FEMA estimates $138M in expected annual loss for a population of 407K.
Beyond physical exposure, Waukesha 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: Waukesha County has received 19 federal disaster declarations since 1969, including 7 for flood events and 6 for severe storm events. The most recent was Severe Storms, Tornadoes, and Flooding (flood), declared in June 2026.
Among 72 Wisconsin counties, Waukesha County ranks #4 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Cold Wave | High | 5.32 / yr | $30M |
| Hail | High | 3.68 / yr | $6M |
| Tornado | High | 0.37 / yr | $24M |
| Heat Wave | Medium | 3.21 / yr | $6M |
| Riverine Flood | Medium | 1.75 / yr | $68M |
| Winter Weather | High | 15.05 / yr | $553K |
| Ice Storm | Medium | 0.63 / yr | $841K |
| Landslide | Low | 0.12 / yr | $6K |
| Lightning | Medium | 36.33 / yr | $606K |
| Earthquake | Very Low | 0.00 / yr | $724K |
| Strong Wind | Medium | 4.13 / yr | $1M |
| Wildfire | Very Low | 0.00 / yr | $83K |
| Drought | Low | 1.23 / yr | $55K |
| Hurricane | Very Low | 0.01 / yr | $3K |
| 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
Waukesha County has received 19 federal disaster declarations since 1969, most recently Severe Storms, Tornadoes, and Flooding in June 2026. Most frequent causes: Flood (7), Severe Storm (6), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| June 2026 | Flood | Severe Storms, Tornadoes, and Flooding |
| September 2025 | Flood | Severe Storms, Straight-Line Winds, Flooding, and Mudslides |
| 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 |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| June 2004 | Severe Storm | Severe Storms and Flooding |
| January 2001 | Snowstorm | Snow |
| June 2000 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
Showing the 10 most recent of 19 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Waukesha County?
Waukesha County has a composite FEMA National Risk Index score of 88.9 out of 100, placing it in the Medium category and the 89th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Waukesha County?
The three highest-rated hazards are Cold Wave (High, $30M EAL), Hail (High, $6M EAL), Tornado (High, $24M EAL). These account for most of the county's expected annual losses.
How does Waukesha County compare to other Wisconsin counties?
Waukesha County ranks #4 of 72 Wisconsin counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Waukesha County had?
FEMA records 19 federal disaster declarations for Waukesha County since 1969, most often 7 for flood events and 6 for severe storm 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. Waukesha County's $138M EAL is a statistical average, not a guarantee for any specific year or address.