McHenry County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within McHenry County: 7.
2. Weak tornadoes were under-recorded before Doppler radar coverage became national in the early 1990s, so earlier decades read low. Ratings use the Fujita scale before February 2007 and the Enhanced Fujita scale after.

Storm Prediction Center severe weather database, 1950 to 2025.

Smoke overhead

1. A smoke day is a date on which a smoke plume traced by NOAA Hazard Mapping System analysts from satellite imagery covered this place's point (the county's population centre or the city centre). Counts here are of medium or heavy smoke. Since 2018 analysts have often drawn light smoke as one area over most of the continent, so light-smoke counts are not comparable from year to year. The plumes show smoke anywhere in the air above, not air quality at the ground, and smoke hidden by cloud is missed.

NOAA Hazard Mapping System smoke analysis, 2011 to 2026, retrieved October 30, 2026.

Claims by ZIP code

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026. NOAA Storm Events through 2026.

River crests

River gauges

1. Crests are the highest and the recent crests the National Weather Service lists for each river gauge in the county that has a flood stage, not every flood. Flood categories use each gauge's current flood stages; crests from before levees, dams or channel changes may not be comparable. Crests measured on an old datum are left out of the rankings.

NOAA National Water Prediction Service gauge records, retrieved October 30, 2026.

1. The Palmer Drought Severity Index is computed by NOAA each month from the county's average temperature and precipitation, relative to the county's own climate. Zero is normal; -3 or lower is severe drought and -4 or lower extreme drought. It describes the long-term balance of moisture, not water supply or crop losses.

NOAA NCEI nClimDiv county Palmer Drought Severity Index, 1895 to September 2026, issued October 6, 2026.

Every earthquake of magnitude 4 or more within 50 miles

1. Earthquakes of magnitude 2.5 or more in the USGS Comprehensive Catalog since 1900. Within 50 miles means the epicentre lies within 50 miles of the county boundary (or inside the county).
2. Small earthquakes were under-recorded before the modern seismic networks of the 1970s and are still missed in remote areas, so early decades read low. Magnitudes are as the catalogue reports them and mix scales (moment, local and body-wave).

USGS ANSS Comprehensive Earthquake Catalog, 1900 to present, retrieved October 30, 2026.

More event types since 1996

Costliest events since 1996

1. Jul 12, 2017Flood$3.9 million
   National Weather Service narrative

   Heavy rain fell across McHenry County and southeast Wisconsin between July 11th and July 13th which lead to major flooding along the Fox River. The river gage at the McHenry Lock & Dam crested at 7.60 feet on July 22nd, the second highest crest on record. Flood stage at the McHenry Lock & Dam is 4 feet. The river gage at the Algonquin Tailwater measured a record crest of 13.15 feet on July 24th. Flood stage at the Algonquin Tailwater is 9.5 feet. There were 557 homes affected with some amount of water from the river flooding.

2. Jan 7, 2008Tornado$2.0 million
   National Weather Service narrative

   A tornado touched down at 330 pm CST about 1.2 miles north of Poplar Grove in Boone County and ended at 348 pm about 3.2 miles north northeast of Harvard in McHenry County. The tornado crossed the Boone McHenry County line near Hunter Road, about 2.1 miles west northwest of Chemung. The tornado crossed Hunter Road into McHenry County and continued to track northeast across Ryan Road as an EF0 and caused mainly minor tree damage. It crossed White Oaks Road then it uprooted a hardwood tree and snapped off pine trees at their base along Maxon Road. This damage continued to be EF0 damage with winds estimated to 80 mph. The tornado intensified as it moved toward the town of Lawrence,…

3. Aug 7, 2007Flash Flood$500,000
   National Weather Service narrative

   Intersection of Route 47 and 120 closed due to two feet of standing water. Willow and Clay Streets closed due to waist deep water. Police conducting rescues from stranded vehicles. Basement flooding was reported throughout Woodstock, and as many as 10 properties were flooded as a creek overflowed its banks in McHenry, IL.

4. Aug 7, 2007Flood$500,000
   National Weather Service narrative

   Flooding continued from heavy rain and flash flooding from earlier on August 7th. Boot Creek overflowed at Hemmingson Road. Picnic tables floating near a car barn in three feet of water. Water flowing over the railway station platform. Many streets are closed due to flooding in Union. Marengo measured 5.10 inches of rain and Woodstock measured 4.35 inches of rain.

5. Jun 13, 2008Flood$250,000
   National Weather Service narrative

   After a wet winter and spring, heavy rain fell in June causing moderate to major flooding on the Des Plaines and Fox Rivers in Lake and McHenry Counties in IL. June rainfall totals included 7.13 inches at Woodstock, 6.56 inches at Spring Grove, and 5.57 inches at Mundelein. Some parts of southern Wisconsin received 10 inches or more. Moderate flooding occurred on the Des Plaines at Russell from the 11th through the 13th mostly impacting park land. On the Fox River, the New Munster, WI river gage reached a record crest of 15.18 feet on the 15th. The gage at McHenry Lock and Dam tailwater crested at 6.8 feet on the 18th. This was the third highest on record. A total of 408…

6. Jul 17, 2006Thunderstorm Wind$200,000
   National Weather Service narrative

   Extensive tree damage was reported across Crystal Lake. Numerous trees, tree limbs and power lines were blown down. One home on Crystal Beach Avenue was deemed uninhabitable because of tree damage.

7. Aug 5, 1996Lightning$200,000
   National Weather Service narrative

   Lightning strikes knocked out power at the Woodstock swimming pool and struck power lines and equipment in 25 different places throughout McHenry County. The roof of an apartment building caught fire after being struck by lightning, with damages estimated at $200,000.00.

8. Jul 27, 2011Lightning$175,000
   National Weather Service narrative

   Lightning started a fire which destroyed the roof of a 2200 square foot home on Glenhurst Court.

9. Jul 27, 2011Lightning$175,000
   National Weather Service narrative

   Lightning started a fire which destroyed the rood of a 2200 square foot home on Glenhurst Court.

10. May 30, 2008High Wind, Mchenry$100,000
    National Weather Service narrative

    A wind gust to 64 mph was measured in Island Lake. In Woodstock, a tree was blown down on a house near Birch and Julie Streets, a four foot diameter tree was blown along with powerlines and a lightpole was blown down near Route 47 and Route 120. In Marengo, a large tree was blown near Forest Street and Highway 23 and a semi truck was overturned near Route 20 and Interstate 90. A large tree was blown down onto a house along with numerous trees blown down between Garden Prairie Road and Illinois 23, six miles north of Marengo. Tree limbs and powerlines were blown down near McHenry.

1. Storm Events records before 1996 cover only tornadoes, thunderstorm wind and hail. Damage figures are as reported by the National Weather Service at the time, not adjusted for inflation.

NOAA NCEI Storm Events Database, 1950 to 2026, issued October 26, 2026.

All-time high

103°FJul 1, 1910

All-time low

−27°FJan 20, 1985

Warmest night

80°FJul 14, 1995

Coldest day

−14°F2 times, most recently Jan 31, 2019

Wettest day

6.47 inJul 24, 2010

Snowiest day

16.5 inJan 13, 1966

Hottest year

2005mean 53.3°F

Coldest year

1979mean 45.2°F

Wettest year

192552.99 in

Driest year

200519.84 in

Snowiest season

100.1 in1978-79

Station Elgin Water (USC00112736), 745 ft elevation, 14.7 miles from the population centre. Daily records from 1897 to October 27, 2026; 97.5% of days in the last 30 years are complete. Records at a single station can differ from a city’s official threaded record, which may combine several stations.

NOAA NCEI Global Historical Climatology Network Daily.

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA Disaster Declarations Summaries, retrieved October 30, 2026. Statewide declarations are not listed.

Neighbouring counties

• Tornadoes NOAA Storm Prediction Center severe weather database, through 2025.
• Tropical cyclones NOAA National Hurricane Center HURDAT2 (Atlantic; Northeast and Central Pacific), through 2025.
• Wildfire USGS/USFS Monitoring Trends in Burn Severity, through 2026.
• Storm events NOAA NCEI Storm Events Database, through 2026.
• Flood insurance OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026.
• Declarations OpenFEMA Disaster Declarations Summaries v2, retrieved October 30, 2026.
• Weather records NOAA NCEI Global Historical Climatology Network Daily, station USC00112736.
• River crests NOAA National Weather Service, National Water Prediction Service river gauges, retrieved October 30, 2026.
• Drought NOAA NCEI nClimDiv county Palmer Drought Severity Index, through September 2026.
• Smoke NOAA NESDIS Hazard Mapping System smoke analysis, retrieved October 30, 2026.
• Earthquakes USGS ANSS Comprehensive Earthquake Catalog (ComCat), retrieved October 30, 2026.

Joins, thresholds and known limits are set out in the methodology. Found an error? Report it. Page built October 30, 2026.