Illinois Power Outage Season
When outages happen most in Illinois, and what to expect.
June is historically Illinois's busiest month for recorded power outages, part of a summer season (June–August) that accounts for about 32% of all recorded outages statewide, averaging 2.8 hours per event. 3 of Illinois's 102 tracked counties currently carry a Reliability Grade of F.
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Illinois outages by month
Total recorded events and average duration per event, summed across every tracked county in Illinois.
Peak season insight
Illinois's outage season runs June–August, accounting for 32% of all recorded outages. June has the highest frequency.
Month-by-month data table
| Month | Events | Avg duration |
|---|---|---|
| January | 3,575 | 2.8 hrs |
| February | 3,519 | 2.7 hrs |
| March | 4,688 | 2.5 hrs |
| April | 5,036 | 2.5 hrs |
| May | 5,712 | 2.7 hrs |
| June | 7,141 | 3.6 hrs |
| July | 6,715 | 3.6 hrs |
| August | 5,235 | 3.4 hrs |
| September | 4,386 | 2.1 hrs |
| October | 4,327 | 1.9 hrs |
| November | 4,513 | 2.2 hrs |
| December | 3,912 | 2.5 hrs |
This month in Illinois
October has historically recorded 4,327 outage events across Illinois, below the state's typical monthly average. Outages that start in October have averaged 1.9 hours.
Main causes by season
Named storms behind Illinois's worst recorded outages, from the NOAA Storm Events Database.
Winter (December–February)
- Ice Storm
- Heavy Snow
- Winter Storm
- Dense Fog
- Tornado
Spring (March–May)
- Thunderstorm Wind
- Hail
- Tornado
- Strong Wind
- Flood
Summer (June–August)
- Hail
- Dense Fog
- Thunderstorm Wind
- Drought
- Excessive Heat
Fall (September–November)
- Drought
- Tornado
- Thunderstorm Wind
- Blizzard
- Winter Storm
Illinois's worst outage events on record
The five largest outages in Illinois by duration and customers affected.
| Date | Duration | Customers affected | Cause |
|---|---|---|---|
| Jul 15, 2024 | 139 hrs | 155,204 (6%) | Flash Flood |
| Jun 29, 2023 | 220 hrs | 48,681 (35%) | Drought |
| Aug 10, 2020 | 148 hrs | 56,765 (68%) | Thunderstorm Wind |
| Aug 11, 2020 | 43 hrs | 163,464 (7%) | Thunderstorm Wind |
| Jul 16, 2024 | 94 hrs | 62,498 (21%) | Thunderstorm Wind |
Highest-risk counties in Illinois
Lowest reliability percentile among Illinois's tracked counties.
| County | Grade | National percentile |
|---|---|---|
| Mercer County | F | 11th |
| Stark County | F | 13th |
| Henderson County | F | 19th |
| Marshall County | D | 22nd |
| Putnam County | D | 26th |
Live weather alerts for Illinois
Flood Watch
Flood Watch issued October 1 at 4:23AM CDT until October 2 at 1:00AM CDT by NWS Quad Cities IA IL
Read the official NWS alert →Flood Watch
Flood Watch issued September 30 at 9:30PM CDT until October 3 at 7:00PM CDT by NWS Chicago IL
Read the official NWS alert →Flood Warning
Flood Warning issued September 30 at 9:30PM CDT by NWS Chicago IL
Read the official NWS alert →These live alerts come from the National Weather Service. They are public-safety information, not an outage prediction.
Illinois power outage FAQ
When do power outages happen most in Illinois?
June is historically the busiest single month for recorded outages in Illinois, and Summer (June–August) accounts for about 32% of all recorded outages across the state.
How long do power outages in Illinois typically last?
Across Illinois's tracked counties, the average recorded outage lasts about 2.8 hours, though individual events -- especially named storms -- can run much longer.
Which counties in Illinois have the highest outage risk?
Mercer County, Stark County, Henderson County, Marshall County, Putnam County currently rank lowest for reliability in Illinois. See each county's page for its full history.
Does this page predict a power outage in Illinois?
No. It describes patterns in recorded county-level outage history, not a guaranteed future event. Check the live National Weather Service alerts below for current conditions.
Prepare for Illinois's outage season
Sized for Illinois's recorded outage frequency and duration.
