National Weather ServiceIllinoisFlash Flood WarningArchive to October 1, 2026
Flash Flood Warnings in Illinois
The National Weather Service issued 134 flash flood warnings for Illinois in 2025 and 129 a year on average in 2008-2025; in 2021-2025 it had the 17th most of any state. 2026 through September: 218, 76% above the average of 124 for those months in 2008-2025. Cook was covered most often (162 times since 2008).
How many flash flood warnings does Illinois get?
Every flash flood warning that covered part of Illinois. 2026 is an outline: the year is not over.
The numbers
| Year | Count |
|---|---|
| 2026 (through September) | 218 |
| 2025 | 134 |
| 2024 | 110 |
| 2023 | 85 |
| 2022 | 119 |
| 2021 | 99 |
| 2020 | 140 |
| 2019 | 148 |
| 2018 | 106 |
| 2017 | 90 |
| 2016 | 115 |
| 2015 | 206 |
| 2014 | 104 |
| 2013 | 147 |
| 2012 | 42 |
| 2011 | 205 |
| 2010 | 153 |
| 2009 | 151 |
| 2008 | 169 |
Source: Iowa Environmental Mesonet archive of National Weather Service watches, warnings and advisories (VTEC); National Weather Service. Data as of October 1, 2026.
When in the year does Illinois get them?
Sum of 2008-2025; the busiest month is labelled.
Source: Iowa Environmental Mesonet archive of National Weather Service watches, warnings and advisories (VTEC); National Weather Service. Data as of October 1, 2026.
Where in Illinois?
| County or forecast zone | Since 2008 | Since 2023 | Last issued |
|---|---|---|---|
| Cook | 162 | 45 | August 1, 2026 |
| Will | 111 | 31 | August 12, 2026 |
| Sangamon | 94 | 25 | August 14, 2026 |
| DuPage | 93 | 25 | August 1, 2026 |
| St. Clair | 92 | 19 | July 11, 2026 |
| Madison | 89 | 20 | June 8, 2026 |
| Tazewell | 89 | 16 | August 19, 2026 |
| Fayette | 86 | 19 | June 21, 2026 |
| Effingham | 84 | 16 | July 27, 2026 |
| Fulton | 83 | 13 | August 15, 2026 |
| Champaign | 82 | 19 | August 20, 2026 |
| Clay | 82 | 17 | July 27, 2026 |
The NWS issues these products for counties or forecast zones; a zone can be part of a county or a mountain range.
Source: Iowa Environmental Mesonet archive of National Weather Service watches, warnings and advisories (VTEC); National Weather Service. Data as of October 1, 2026.
The latest flash flood warnings for Illinois in AreaZine's record
NWS ChicagoWarningSeptember 20, 2026
Flash Flood Warning: De Kalb, La Salle and Lee, IL
Expired 8:00 a.m. CDT, September 20, 2026
NWS Quad Cities IAWarningSeptember 20, 2026
Flash Flood Warning: Clinton, Muscatine, Scott and 5 more, IA and IL
Expired 7:30 a.m. CDT, September 20, 2026
NWS Quad Cities IAWarningSeptember 19, 2026
Flash Flood Warning: Dubuque, Jackson, Jo Daviess and 1 more, IA and IL
Expired 10:15 a.m. CDT, September 19, 2026
NWS ChicagoWarningSeptember 17, 2026
Flash Flood Warning: De Kalb, La Salle and Lee, IL
Expired 11:00 a.m. CDT, September 17, 2026
NWS LincolnWarningAugust 21, 2026
Flash Flood Warning: Marshall, IL
Expired 11:45 p.m. CDT, August 21, 2026
NWS ChicagoWarningAugust 21, 2026
Flash Flood Warning: La Salle, IL
Expired 12:00 a.m. CDT, August 22, 2026
NWS PaducahWarningAugust 19, 2026
Flash Flood Warning: Pulaski, Ballard and Mississippi County, IL and KY
Expired 6:00 a.m. CDT, August 20, 2026
NWS PaducahWarningAugust 19, 2026
Flash Flood Warning: Alexander, Scott and Stoddard, IL and MO
Expired 5:45 a.m. CDT, August 20, 2026
This list is AreaZine's record of the NWS alert feed, kept since April 6, 2026; the counts above come from the complete IEM archive.
Source: National Weather Service alerts (api.weather.gov).
What is a flash flood warning?
A flash flood warning means flash flooding is happening or about to happen: water rising fast in streams, streets or dry washes, usually within six hours of heavy rain or a dam or levee failure. A warning means the hazard is happening, about to happen, or very likely: act now to protect people and property. The national record · Every warning type in Illinois.