McHenry County, Illinois Natural Disaster Risk
FEMA National Risk Index assessment · IL
MediumComposite Risk Score
National percentile: 91th
McHenry County faces medium composite natural disaster risk (NRI Risk Index score 90.8, 91th national percentile), driven primarily by cold wave and tornado exposure. Expected annual loss across all 18 hazard types is $142M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in McHenry County is medium, with a National Risk Index score of 90.8 out of 100 — placing it in the 91st 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 — $23M in expected annual loss and about 5.69 events per year; tornado (violently rotating columns of air capable of catastrophic local damage) at High risk — $25M in expected annual loss and about 0.44 events per year; and riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at Medium risk — $85M in expected annual loss and about 1.11 events per year. Across all hazards, FEMA estimates $142M in expected annual loss for a population of 310K.
Beyond physical exposure, McHenry 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.
History supports the rating: McHenry County has received 16 federal disaster declarations since 1965, including 6 for snowstorm events and 5 for flood events. The most recent was Covid-19 Pandemic (biological), declared in March 2020.
Among 102 Illinois counties, McHenry County ranks #10 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Cold Wave | High | 5.69 / yr | $23M |
| Tornado | High | 0.44 / yr | $25M |
| Riverine Flood | Medium | 1.11 / yr | $85M |
| Strong Wind | High | 6.27 / yr | $3M |
| Hail | Medium | 4.84 / yr | $1M |
| Winter Weather | Medium | 14.59 / yr | $310K |
| Heat Wave | Low | 2.79 / yr | $2M |
| Earthquake | Low | 0.00 / yr | $2M |
| Lightning | Medium | 39.18 / yr | $871K |
| Drought | Low | 8.59 / yr | $420K |
| Landslide | Very Low | 0.11 / yr | $3K |
| Ice Storm | Low | 0.61 / yr | $171K |
| Wildfire | Very Low | 0.00 / yr | $25K |
| 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
McHenry County has received 16 federal disaster declarations since 1965, most recently Covid-19 Pandemic in March 2020. Most frequent causes: Snowstorm (6), Flood (5), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| May 2013 | Flood | Severe Storms, Straight-Line Winds, and Flooding |
| March 2011 | Snowstorm | Severe Winter Storm and Snowstorm |
| March 2008 | Snowstorm | Record Snow and Near Record Snow |
| December 2006 | Snowstorm | Snow |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| January 2001 | Snowstorm | Illinois Winter Snow Storms |
| January 1999 | Snowstorm | Il-Winter Storm 1/1/99 |
| July 1993 | Flood | Severe Storms & 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 McHenry County?
McHenry County has a composite FEMA National Risk Index score of 90.8 out of 100, placing it in the Medium category and the 91th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in McHenry County?
The three highest-rated hazards are Cold Wave (High, $23M EAL), Tornado (High, $25M EAL), Riverine Flood (Medium, $85M EAL). These account for most of the county's expected annual losses.
How does McHenry County compare to other Illinois counties?
McHenry County ranks #10 of 102 Illinois counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has McHenry County had?
FEMA records 16 federal disaster declarations for McHenry County since 1965, most often 6 for snowstorm events and 5 for flood events. The most recent was Covid-19 Pandemic, declared in March 2020.
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. McHenry County's $142M EAL is a statistical average, not a guarantee for any specific year or address.