National Weather ServiceIllinoisExtreme Heat WatchArchive to October 1, 2026
Extreme Heat Watches in Illinois
The National Weather Service issued 8 extreme heat watches for Illinois in 2025 and 3 a year on average in 2008-2025; in 2021-2025 it had the 19th most of any state. 2026 through September: 9, 189% above the average of 3 for those months in 2008-2025. St. Clair was covered most often (15 times since 2008).
How many extreme heat watches does Illinois get?
Every extreme heat watch that covered part of Illinois. 2026 is an outline: the year is not over.
The numbers
| Year | Count |
|---|---|
| 2026 (through September) | 9 |
| 2025 | 8 |
| 2024 | 3 |
| 2023 | 8 |
| 2022 | 0 |
| 2021 | 0 |
| 2020 | 0 |
| 2019 | 6 |
| 2018 | 3 |
| 2017 | 4 |
| 2016 | 4 |
| 2015 | 0 |
| 2014 | 1 |
| 2013 | 0 |
| 2012 | 3 |
| 2011 | 11 |
| 2010 | 4 |
| 2009 | 1 |
| 2008 | 0 |
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 |
|---|---|---|---|
| St. Clair | 15 | 6 | August 31, 2026 |
| Madison | 15 | 6 | August 31, 2026 |
| Rock Island | 13 | 7 | July 27, 2026 |
| Mercer | 13 | 7 | July 27, 2026 |
| Washington | 12 | 5 | August 31, 2026 |
| Warren | 12 | 6 | July 27, 2026 |
| Putnam | 12 | 6 | July 27, 2026 |
| Monroe | 12 | 6 | August 31, 2026 |
| McDonough | 12 | 6 | July 27, 2026 |
| Henry | 12 | 6 | July 27, 2026 |
| Henderson | 12 | 6 | July 27, 2026 |
| Hancock | 12 | 6 | 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.
What is an extreme heat watch?
An extreme heat watch means dangerous heat is possible in the coming days. It replaced the excessive heat watch in 2025. A watch means the conditions for the hazard are possible or favourable, but it is not yet happening: be ready to act if a warning follows. AreaZine's counts include the excessive heat watches issued before the change. The national record · Every warning type in Illinois.