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Flood in McHenry County, Illinois
48 floods and flash floods events in the NCEI Storm Events record, 1950 to 2026. Event types counted: Flood, Flash Flood, Coastal Flood, Lakeshore Flood.
NCEI notes that Storm Data is compiled from a variety of sources including the National Weather Service, other federal, state and local agencies, the media and the public; that property and crop damage figures are estimates; and that some events are recorded by NWS forecast zone rather than by county. FEMA notes that NFIP claim records are redacted and aggregated to protect the privacy of policyholders. Storm records through 30 Jun 2026.
NCEI records 48 flood events in McHenry County, Illinois, between 1950 and 2026, spread over 21 years.
June is the busiest month, with 17 of the recorded events. The last 20 years account for 35 events against 13 in the 20 years before, a change that reflects reporting practice as much as weather.
The county holds 0.7% of the 6,507 flood events recorded in Illinois; its 8.0 per 100 square miles compares with 11.7 statewide.
Compared with Illinois
| Measure | McHenry County | Illinois | US |
|---|---|---|---|
| Flood events since 1950 | 48 | 6,507 | 183,559 |
| Per 100 square miles | 8.0 | 11.7 | 5.2 |
| Per 10,000 residents | 1.5 | 5.1 | 5.5 |
| Deaths recorded | 0 | 61 | 2,961 |
| Busiest month | June | June | June |
By year
Seasonality
0Feb
1Mar
1Apr
2May
8Jun
17Jul
5Aug
7Sep
7Oct
0Nov
0Dec
0
Recorded events
All 48 events, most recent first. Magnitude is hail size, tornado rating or wind speed as recorded.
| Date | Event type | Magnitude | Property damage | Crop damage | Deaths | Injuries | Geography |
|---|---|---|---|---|---|---|---|
| 11 Jun 2026 | Flash Flood | — | — | — | — | — | County |
| 11 Jun 2026 | Flood | — | — | — | — | — | County |
| 11 Jun 2026 | Flood | — | — | — | — | — | County |
| 17 Apr 2026 | Flood | — | — | — | — | — | County |
| 17 Apr 2026 | Flood | — | — | — | — | — | County |
| 22 Jun 2024 | Flash Flood | — | — | — | — | — | County |
| 7 May 2024 | Flood | — | — | — | — | — | County |
| 5 Jul 2022 | Flash Flood | — | — | — | — | — | County |
| 5 Jul 2022 | Flood | — | — | — | — | — | County |
| 24 Aug 2021 | Flash Flood | — | — | — | — | — | County |
| 29 Jun 2020 | Flood | — | — | — | — | — | County |
| 23 May 2020 | Flood | — | — | — | — | — | County |
| 14 May 2020 | Flash Flood | — | — | — | — | — | County |
| 13 Sep 2019 | Flash Flood | — | — | — | — | — | County |
| 12 Sep 2019 | Flash Flood | — | — | — | — | — | County |
| 3 Sep 2018 | Flood | — | — | — | — | — | County |
| 3 Sep 2018 | Flood | — | — | — | — | — | County |
| 2 Sep 2018 | Flood | — | — | — | — | — | County |
| 12 Jul 2017 | Flood | — | $3.9M | — | — | — | County |
| 28 Jun 2017 | Flash Flood | — | — | — | — | — | County |
| 14 Jun 2017 | Flood | — | — | — | — | — | County |
| 14 Jun 2017 | Flood | — | — | — | — | — | County |
| 14 Jun 2017 | Flood | — | — | — | — | — | County |
| 26 Jun 2013 | Flash Flood | — | — | — | — | — | County |
| 26 Jun 2013 | Flash Flood | — | — | — | — | — | County |
| 17 Mar 2012 | Flood | — | — | — | — | — | County |
| 11 May 2011 | Flood | — | — | — | — | — | County |
| 11 May 2011 | Flood | — | — | — | — | — | County |
| 13 Sep 2008 | Flash Flood | — | — | — | — | — | County |
| 13 Jun 2008 | Flood | — | $250K | — | — | — | County |
| 19 Aug 2007 | Flash Flood | — | $50K | — | — | — | County |
| 19 Aug 2007 | Flash Flood | — | — | — | — | — | County |
| 7 Aug 2007 | Flash Flood | — | $500K | — | — | — | County |
| 7 Aug 2007 | Flood | — | $500K | — | — | — | County |
| 9 Jul 2007 | Flood | — | — | — | — | — | County |
| 20 Jul 2006 | Flood | — | — | — | — | — | County |
| 19 May 2005 | Flood | — | — | — | — | — | Forecast zone |
| 11 Jun 2004 | Flood | — | — | — | — | — | Forecast zone |
| 18 May 2004 | Flash Flood | — | — | — | — | — | County |
| 19 Sep 2002 | Flood | — | — | — | — | — | County |
| 22 Aug 2002 | Flood | — | — | — | — | — | Forecast zone |
| 22 Aug 2002 | Flash Flood | — | — | — | — | — | County |
| 4 Jun 2002 | Flood | — | — | — | — | — | Forecast zone |
| 12 Jun 2000 | Flash Flood | — | — | — | — | — | County |
| 12 Jun 2000 | Flood | — | — | — | — | — | Forecast zone |
| 13 Jun 1999 | Flood | — | — | — | — | — | Forecast zone |
| 20 Feb 1997 | Flood | — | — | — | — | — | Forecast zone |
| 20 May 1996 | Flash Flood | — | — | — | — | — | County |
Questions and answers
How many flood events has McHenry County had?
48 events in the NCEI Storm Events record between 1950 and 2026. Reporting of floods and flash floods became far more complete after 1996, so early decades undercount.
When was the last recorded flood event in McHenry County?
11 Jun 2026 (Flood). Records reach NCEI about 120 days after the month ends.
What was the most damaging flood event recorded in McHenry County?
The flood of 12 Jul 2017, with property damage estimated by NCEI at $3.9M.
How does McHenry County compare with Illinois for flood?
8.0 events per 100 square miles against 11.7 statewide; the county holds 48 of the state's 6,507 recorded events.
Provenance
NOAA NCEI Storm Events Database, yearly details files through 30 Jun 2026, public domain. County-recorded events plus zone-recorded events whose forecast zone is named for the county (marked "Forecast zone"). Population and area from the US Census Bureau (2021). Built 1 Oct 2026. See the methodology, the Flood hub and the county page.