Washtenaw County, Michigan Natural Disaster Risk
FEMA National Risk Index assessment · MI
MediumComposite Risk Score
National percentile: 89th
Washtenaw County faces medium composite natural disaster risk (NRI Risk Index score 89.3, 89th national percentile), driven primarily by strong wind and tornado exposure. Expected annual loss across all 18 hazard types is $93M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Washtenaw County at medium composite risk, with a National Risk Index score of 89.3 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 Washtenaw County's expected losses come from strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at High risk — $6M in expected annual loss and about 5.70 events per year; tornado (violently rotating columns of air capable of catastrophic local damage) at High risk — $21M in expected annual loss and about 0.35 events per year; and cold wave (prolonged spells of dangerously low temperatures) at High risk — $11M in expected annual loss and about 2.79 events per year. Across all hazards, FEMA estimates $93M in expected annual loss for a population of 372K.
Beyond physical exposure, Washtenaw County has a 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: Washtenaw County has received 12 federal disaster declarations since 1965, including 3 for snowstorm events and 2 for flood events. The most recent was Severe Storms, Tornadoes, and Flooding (flood), declared in June 2026.
Among 83 Michigan counties, Washtenaw County ranks #6 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Strong Wind | High | 5.70 / yr | $6M |
| Tornado | High | 0.35 / yr | $21M |
| Cold Wave | High | 2.79 / yr | $11M |
| Ice Storm | High | 1.78 / yr | $1M |
| Riverine Flood | Medium | 1.18 / yr | $47M |
| Lightning | High | 36.85 / yr | $1M |
| Heat Wave | Medium | 3.68 / yr | $3M |
| Hail | Medium | 3.14 / yr | $1M |
| Earthquake | Low | 0.00 / yr | $1M |
| Winter Weather | Medium | 10.47 / yr | $179K |
| Landslide | Low | 0.18 / yr | $7K |
| Hurricane | Very Low | 0.01 / yr | $73K |
| Wildfire | Very Low | 0.00 / yr | $38K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Drought | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Washtenaw County has received 12 federal disaster declarations since 1965, most recently Severe Storms, Tornadoes, and Flooding in June 2026. Most frequent causes: Snowstorm (3), Flood (2), Severe Storm (2).
| Declared | Type | Disaster |
|---|---|---|
| June 2026 | Flood | Severe Storms, Tornadoes, and Flooding |
| July 2021 | Severe Storm | Severe Storms, Flooding, and Tornadoes |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| June 2004 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| September 2003 | Other | Power Outage |
| January 2001 | Snowstorm | Snow |
| January 1999 | Snowstorm | Mi - Severe Weather 1/2 /99 |
| September 1980 | Flood | Severe Storms & Flooding |
Showing the 10 most recent of 12 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Washtenaw County?
Washtenaw County has a composite FEMA National Risk Index score of 89.3 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 Washtenaw County?
The three highest-rated hazards are Strong Wind (High, $6M EAL), Tornado (High, $21M EAL), Cold Wave (High, $11M EAL). These account for most of the county's expected annual losses.
How does Washtenaw County compare to other Michigan counties?
Washtenaw County ranks #6 of 83 Michigan counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Washtenaw County had?
FEMA records 12 federal disaster declarations for Washtenaw County since 1965, most often 3 for snowstorm events and 2 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. Washtenaw County's $93M EAL is a statistical average, not a guarantee for any specific year or address.