National Weather ServiceIllinoisHeat AdvisoryArchive to October 1, 2026
Heat Advisories in Illinois
The National Weather Service issued 34 heat advisories for Illinois in 2025 and 25 a year on average in 2008-2025; in 2021-2025 it had the 19th most of any state. 2026 through September: 50, 102% above the average of 25 for those months in 2008-2025. Hancock was covered most often (104 times since 2008).
How many heat advisories does Illinois get?
Every heat advisory that covered part of Illinois. 2026 is an outline: the year is not over.
The numbers
| Year | Count |
|---|---|
| 2026 (through September) | 50 |
| 2025 | 34 |
| 2024 | 29 |
| 2023 | 18 |
| 2022 | 43 |
| 2021 | 30 |
| 2020 | 15 |
| 2019 | 14 |
| 2018 | 29 |
| 2017 | 16 |
| 2016 | 15 |
| 2015 | 18 |
| 2014 | 12 |
| 2013 | 8 |
| 2012 | 31 |
| 2011 | 48 |
| 2010 | 55 |
| 2009 | 20 |
| 2008 | 10 |
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 |
|---|---|---|---|
| Hancock | 104 | 27 | August 31, 2026 |
| Henderson | 102 | 26 | August 31, 2026 |
| McDonough | 101 | 25 | August 31, 2026 |
| Alexander | 100 | 28 | September 15, 2026 |
| Pulaski | 100 | 28 | September 15, 2026 |
| Warren | 99 | 24 | August 31, 2026 |
| Massac | 94 | 27 | September 15, 2026 |
| Union | 93 | 29 | September 15, 2026 |
| Mercer | 91 | 21 | August 31, 2026 |
| Jackson | 89 | 27 | September 15, 2026 |
| Johnson | 89 | 26 | September 15, 2026 |
| Williamson | 86 | 24 | September 15, 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 a heat advisory?
A heat advisory means heat that can make people ill, especially those without cooling, below the office's extreme heat warning values. An advisory is issued for a hazard less serious than a warning that can still cause inconvenience or danger if people are not careful. The national record · Every warning type in Illinois.