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Flood in Knox County, Illinois
47 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 47 flood events in Knox County, Illinois, between 1950 and 2026, spread over 17 years.
May is the busiest month, with 16 of the recorded events. The last 20 years account for 34 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 6.6 per 100 square miles compares with 11.7 statewide.
Compared with Illinois
| Measure | Knox County | Illinois | US |
|---|---|---|---|
| Flood events since 1950 | 47 | 6,507 | 183,559 |
| Per 100 square miles | 6.6 | 11.7 | 5.2 |
| Per 10,000 residents | 9.5 | 5.1 | 5.5 |
| Deaths recorded | 0 | 61 | 2,961 |
| Busiest month | May | June | June |
By year
Seasonality
0Feb
2Mar
2Apr
3May
16Jun
14Jul
7Aug
0Sep
2Oct
1Nov
0Dec
0
Recorded events
All 47 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 |
|---|---|---|---|---|---|---|---|
| 10 Jun 2026 | Flash Flood | — | — | — | — | — | County |
| 8 Jun 2026 | Flash Flood | — | — | — | — | — | County |
| 8 Jul 2022 | Flash Flood | — | — | — | — | — | County |
| 8 Jul 2022 | Flash Flood | — | — | — | — | — | County |
| 6 Jun 2022 | Flash Flood | — | — | — | — | — | County |
| 28 May 2019 | Flash Flood | — | — | — | — | — | County |
| 7 Sep 2018 | Flash Flood | — | — | — | — | — | County |
| 14 Oct 2017 | Flash Flood | — | — | — | — | — | County |
| 16 Jul 2015 | Flash Flood | — | — | — | — | — | County |
| 11 Jul 2015 | Flash Flood | — | — | — | — | — | County |
| 14 Jun 2015 | Flash Flood | — | — | — | — | — | County |
| 10 Jun 2015 | Flash Flood | — | — | — | — | — | County |
| 7 Jun 2015 | Flash Flood | — | — | — | — | — | County |
| 4 Sep 2014 | Flash Flood | — | — | — | — | — | County |
| 28 May 2013 | Flash Flood | — | $1.0M | — | — | — | County |
| 28 May 2013 | Flood | — | — | — | — | — | County |
| 27 May 2013 | Flood | — | — | — | — | — | County |
| 26 May 2013 | Flash Flood | — | — | — | — | — | County |
| 18 Apr 2013 | Flash Flood | — | $40M | — | — | — | County |
| 18 Apr 2013 | Flood | — | — | — | — | — | County |
| 29 May 2011 | Flash Flood | — | $100K | — | — | — | County |
| 25 May 2011 | Flash Flood | — | — | — | — | — | County |
| 23 Jun 2010 | Flash Flood | — | — | — | — | — | County |
| 22 Jun 2010 | Flash Flood | — | — | — | — | — | County |
| 18 Jun 2010 | Flash Flood | — | — | — | — | — | County |
| 1 Jun 2010 | Flash Flood | — | — | — | — | — | County |
| 13 May 2010 | Flash Flood | — | — | — | — | — | County |
| 16 May 2009 | Flood | — | — | $1.5M | — | — | County |
| 15 May 2009 | Flash Flood | — | — | — | — | — | County |
| 15 May 2009 | Flood | — | — | — | — | — | County |
| 15 May 2009 | Flash Flood | — | — | — | — | — | County |
| 15 May 2009 | Flash Flood | — | — | — | — | — | County |
| 10 Mar 2009 | Flood | — | — | — | — | — | County |
| 9 Mar 2009 | Flood | — | — | — | — | — | County |
| 22 Jul 2004 | Flash Flood | — | — | — | — | — | County |
| 9 Jul 2004 | Flash Flood | — | — | — | — | — | County |
| 30 May 2004 | Flash Flood | — | — | — | — | — | County |
| 30 Apr 2003 | Flash Flood | — | — | — | — | — | County |
| 27 Jul 2002 | Flash Flood | — | — | — | — | — | County |
| 13 Jun 2002 | Flood | — | — | — | — | — | Forecast zone |
| 12 Jun 2002 | Flash Flood | — | — | — | — | — | County |
| 4 Jun 2002 | Flash Flood | — | — | — | — | — | County |
| 11 May 2002 | Flash Flood | — | — | — | — | — | County |
| 11 May 2002 | Flood | — | — | — | — | — | Forecast zone |
| 24 Feb 2001 | Flash Flood | — | — | — | — | — | County |
| 12 Jun 2000 | Flood | — | — | — | — | — | County |
| 21 Feb 1997 | Flood | — | — | — | — | — | Forecast zone |
Questions and answers
How many flood events has Knox County had?
47 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 Knox County?
10 Jun 2026 (Flash Flood). Records reach NCEI about 120 days after the month ends.
What was the most damaging flood event recorded in Knox County?
The flash flood of 18 Apr 2013, with property damage estimated by NCEI at $40M.
How does Knox County compare with Illinois for flood?
6.6 events per 100 square miles against 11.7 statewide; the county holds 47 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.