Power outage history
Cook County Illinois
2.1hours
without power for the average customer in a typical year, 2018–2025
88th most of 101 in Illinois 67% below the national median
Every day since 2015
Eleven years, one night at a time
Each cell is a day. The brighter it is, the larger the share of Cook's customers who were without power at that day's worst moment.
Year by year
Hours in the dark, per customer
2020 was the worst well-recorded year, at 5.6 hours for the average customer. Hatched years have a thin record and are left out of the averages.
Cook, hours without power per customer
The record
The biggest outages since 2015
Ranked by customer-hours lost: customers out multiplied by how long they stayed out. Times are local.
| Began | Storm | Peak out | Share | Lasted | 90% restored | Customer-hours |
|---|---|---|---|---|---|---|
| Aug 10, 2020 | Thunderstorms | 279,858 | 13% | 4.1 d | 6.8 h | 9.6M |
| Jul 15, 2024 | Thunderstorms | 155,204 | 7% | 46 h | 2.1 d | 3.2M |
| Nov 25, 2018 | No storm report | 101,662 | 5% | 38 h | 12 min | 2.0M |
| Jun 13, 2022 | Thunderstorms | 67,114 | 3% | 19 h | 29 h | 799k |
| Feb 19, 2016 | No storm report | 95,661 | 4% | 16 h | 18 h | 798k |
| Aug 10, 2021 | Thunderstorms | 73,829 | 3% | 17 h | 25 h | 737k |
| May 15, 2025 | Thunderstorms | 63,645 | 3% | 13 h | 25 h | 510k |
| Aug 2, 2015 | Thunderstorms | 38,285 | 2% | 12 h | 22 h | 367k |
| Jan 12, 2024 | Winter storm | 73,699 | 3% | 6.5 h | 9.2 h | 320k |
| Aug 17, 2025 | Thunderstorms | 44,656 | 2% | 8.2 h | 18 h | 267k |
| Jul 5, 2022 | Thunderstorms | 31,686 | 1% | 3.2 h | 13 h | 89k |
| Jul 24, 2025 | Thunderstorms | 29,730 | 1% | 3.2 h | 15 h | 84k |
| Jun 9, 2020 | Tropical Storm Cristobal | 31,346 | 1% | 2.5 h | 14 h | 72k |
| Aug 27, 2024 | Thunderstorms | 25,860 | 1% | 3.0 h | 15 h | 72k |
| Feb 22, 2023 | Ice storm | 23,437 | 1% | 2.0 h | 13 h | 40k |
| Aug 29, 2022 | Thunderstorms | 23,698 | 1% | 1.5 h | 7.0 h | 29k |
| Jul 29, 2021 | Thunderstorms | 22,644 | 1% | 48 min | 10 h | 17k |
| May 18, 2017 | Thunderstorms | 22,361 | 1% | 48 min | 13 h | 17k |
After the peak
How fast the lights come back
Each line is one major outage, from its peak. The amber line is the typical path.
When it happens
The outage clock
Customer-hours out by month (rings, January innermost) and local hour, 2018–2025.
What was happening
Weather behind the outages
Each outage is matched to NOAA storm reports for Cook from twelve hours before it began to its peak. Matching shows coincidence, not proof of cause.
- Thunderstorms 86%
- No storm on record 11%
- Winter storm 1.8%
Who keeps the lights on
Utilities serving Cook
As each utility reports to the Energy Information Administration for its whole Illinois territory, not this county alone. Outage minutes include major storm days.
| Utility | Type | Outage min / yr | Excl. major storms | Outages / yr | Residential ¢/kWh | Customers |
|---|---|---|---|---|---|---|
| Commonwealth Edison Co | Investor Owned | 77 | 38 | 0.66 | 17.7 | 3.8M |
| Village of Winnetka | IL | 13 | – | 0.32 | 12.2 | 80k |
| University of Illinois | State | – | – | – | – | – |
EIA Form 861, latest year each utility reported. Outage minutes are SAIDI, the yearly minutes the average customer goes without power; outages a year are SAIFI.
About these numbers
Notes
Outages come from the EAGLE-I record of utility outage maps collected every 15 minutes by Oak Ridge National Laboratory. Hours without power are customer-hours divided by the county's 2,162,007 electricity customers. Averages use well-covered years from 2018. Outages shorter than 15 minutes, and utilities that publish no outage map, are not in the record, so these figures understate the total. How every number is made →