Williamson County, Tennessee Natural Disaster Risk
FEMA National Risk Index assessment · TN
MediumComposite Risk Score
National percentile: 85th
Williamson County faces medium composite natural disaster risk (NRI Risk Index score 85.1, 85th national percentile), driven primarily by cold wave and earthquake exposure. Expected annual loss across all 18 hazard types is $98M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Williamson County carries a medium composite natural disaster risk, with a National Risk Index score of 85.1 out of 100 — placing it in the 85th 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 cold wave (prolonged spells of dangerously low temperatures) at High risk — $13M in expected annual loss and about 1.16 events per year; earthquake (ground shaking from sudden movement along geologic faults) at Low risk — $8M in expected annual loss and about 0.00 events per year; and strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at High risk — $3M in expected annual loss and about 6.11 events per year. Across all hazards, FEMA estimates $98M in expected annual loss for a population of 248K.
Beyond physical exposure, Williamson 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: Williamson County has received 16 federal disaster declarations since 1974, including 8 for severe storm events and 2 for winter storm events. The most recent was Severe Winter Storm (winter storm), declared in February 2026.
Among 95 Tennessee counties, Williamson County ranks #11 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Cold Wave | High | 1.16 / yr | $13M |
| Earthquake | Low | 0.00 / yr | $8M |
| Strong Wind | High | 6.11 / yr | $3M |
| Tornado | Medium | 0.51 / yr | $12M |
| Riverine Flood | Medium | 2.18 / yr | $57M |
| Winter Weather | Medium | 5.16 / yr | $469K |
| Ice Storm | High | 0.62 / yr | $1M |
| Heat Wave | Low | 4.95 / yr | $2M |
| Landslide | Very Low | 0.86 / yr | $3K |
| Lightning | Low | 60.55 / yr | $468K |
| Hail | Low | 3.50 / yr | $332K |
| Hurricane | Very Low | 0.02 / yr | $55K |
| Wildfire | Very Low | 0.00 / yr | $45K |
| Drought | Low | 9.57 / yr | $77K |
| 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
Williamson County has received 16 federal disaster declarations since 1974, most recently Severe Winter Storm in February 2026. Most frequent causes: Severe Storm (8), Winter Storm (2), Tornado (2).
| Declared | Type | Disaster |
|---|---|---|
| February 2026 | Winter Storm | Severe Winter Storm |
| January 2026 | Winter Storm | Severe Winter Storm |
| April 2025 | Severe Storm | Severe Storms, Straight-Line Winds, Tornadoes, and Flooding |
| May 2021 | Tornado | Severe Storms, Tornadoes, and Flooding |
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| May 2010 | Severe Storm | Severe Storms, Flooding, Straight-Line Winds, and Tornadoes |
| February 2008 | Severe Storm | Severe Storms, Tornadoes, Straight-Line Winds, and Flooding |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| May 2003 | Severe Storm | Severe Storms, Tornadoes, 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 Williamson County?
Williamson County has a composite FEMA National Risk Index score of 85.1 out of 100, placing it in the Medium category and the 85th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Williamson County?
The three highest-rated hazards are Cold Wave (High, $13M EAL), Earthquake (Low, $8M EAL), Strong Wind (High, $3M EAL). These account for most of the county's expected annual losses.
How does Williamson County compare to other Tennessee counties?
Williamson County ranks #11 of 95 Tennessee counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Williamson County had?
FEMA records 16 federal disaster declarations for Williamson County since 1974, most often 8 for severe storm events and 2 for winter storm events. The most recent was Severe Winter Storm, declared in February 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. Williamson County's $98M EAL is a statistical average, not a guarantee for any specific year or address.