McHenry County, Illinois

What hazards hit McHenry County most?

The most frequent records are severe thunderstorm wind events: 357 since 1960. 50% of its severe thunderstorm wind events since 1960 fell in June and July. The rank column places the county among Illinois's counties by days with a record per 1,000 square miles of land over each hazard's complete period.

Source: NOAA NCEI Storm Events Database (county and forecast-zone records attributed to the county; a zone record shows its own totals on each county it covers). Days: dates with at least one record of the hazard in the county. Ranks: days with a record per 1,000 square miles of land (Census Bureau 2024 Gazetteer), since 1950 for tornadoes, 1955 for hail and thunderstorm wind, 1996 for the rest.

How many tornadoes has McHenry County had?

NOAA records 27 tornadoes in McHenry County from 1958 to 2026, the strongest rated F4, with 7 deaths and 120 injuries recorded in the county. A tornado that crossed a county line is counted in each county it touched, with the length of its path inside the county.

Counted as whole tornadoes rather than county records, the Storm Prediction Center's database holds 30 tornadoes whose track touched McHenry County since 1950 (NOAA's county records number 27: they file a crossing tornado once per county segment, and the two databases differ on some tracks); along their whole tracks they killed 32 people, 7 of them in McHenry County.

Map of the strongest tornado tracks in Illinois.

Source: NOAA NCEI Storm Events Database, tornado records by county (path length in the county, maximum width); ratings as published: F scale before February 1, 2007, EF scale after. Whole-track figures: NOAA Storm Prediction Center tornado database (1950-2025). SPC severe weather database.

When was the last damaging storm in McHenry County?

The most recent record with damage, injuries or deaths is the June 25, 2024 lightning (1 injury).

An employee of Nichols Farm and Orchard in Marengo was injured when he was struck by lightning. It's believed that lightning struck a tree and then traveled through the man who was nearby. He was transported to the hospital with minor to moderate injuries.
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 1194987)

Source: NOAA NCEI Storm Events Database; every record of 2025-2026 is listed, earlier ones when they caused deaths, injuries or $250,000 of damage (2025 dollars), and every tornado.

The deadliest and costliest records

Source: NOAA NCEI Storm Events Database: deaths and injuries direct and indirect; damage is property plus crops as estimated by the National Weather Service, converted to 2025 dollars.

Is it getting more frequent?

Records per decade for McHenry County's most frequent hazards. Counts rose everywhere after 1996, when NOAA began recording every event type, so compare decades within a hazard's complete period only (the shaded cells come before it).

Source: NOAA NCEI Storm Events Database, records per calendar decade; zone records from the CZ_TYPE field (Z).

What time of year?

50% of its severe thunderstorm wind events since 1960 fell in June and July. The two busiest months are in violet.

Source: NOAA NCEI Storm Events Database, records by the month they began.

Federal disaster declarations for McHenry County

FEMA's register lists 16 declarations that include McHenry County: 9 major disasters, 7 emergencies and 0 fire management assistance declarations. Most were for snowstorm (6) and flood (5).

Source: FEMA OpenFEMA Disaster Declarations Summaries (v2), declarations through October 2, 2026; one declaration is counted once however many areas it names. OpenFEMA dataset page.

How many floods has McHenry County had?

NOAA's Storm Events Database holds 52 flood or flash flood records for McHenry County from 1996 to 2026, on 35 days, with 0 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), McHenry County ranks 333rd of 2,942 U.S. counties.

The National Flood Insurance Program has paid $7.6 million on 987 claims filed in McHenry County; the most in one year was 165 in 2013. Claims count insured losses only: uninsured flood damage is not in this file.

Source: FEMA OpenFEMA NFIP Redacted Claims, as of September 8, 2026; claims by year of loss, payments in the dollars of the year paid. OpenFEMA dataset page.

FEMA's modeled risk for McHenry County

FEMA's National Risk Index rates McHenry County Relatively Moderate overall, with an expected annual loss of $142 million. These are FEMA's model estimates of future loss from 18 hazards, not a count of what happened; they can differ from the record above.

Source: FEMA National Risk Index, county table, December 2025 release. FEMA's National Risk Index map.

Counties that share a border with McHenry County

1. Cook County 3,347
2. Kane County 1,147
3. Walworth County, WI 1,038
4. McHenry County 941
5. Lake County 869
6. Kenosha County, WI 830
7. DeKalb County 654
8. Boone County 419

Source: U.S. Census Bureau county adjacency file; NOAA NCEI Storm Events Database, records since 1950. The Census Bureau's adjacency file.

Next

• Tornadoes in IllinoisEvery Illinois tornado since 1950 and the counties with the most per square mile
• Severe thunderstorm wind in IllinoisThe state's severe thunderstorm wind events, by county, year and month
• The Illinois recordEvery hazard in the state, its deadliest events and its federal declarations
• FEMA's risk rating for each hazard in McHenry CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download McHenry County's FEMA declarations (CSV)16 rows: every declaration that named the county, for your own analysis