Power outage history
Big Horn County Montana
0.9hours
without power for the average customer in a typical year, 2018–2025
35th most of 35 in Montana 86% 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 Big Horn's customers who were without power at that day's worst moment.
Year by year
Hours in the dark, per customer
2024 was the worst well-recorded year, at 2.6 hours for the average customer. Hatched years have a thin record and are left out of the averages.
Big Horn, 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 |
|---|---|---|---|---|---|---|
| Jul 10, 2024 | No storm report | 102 | 1% | 6.1 d | – | 14k |
| Jun 11, 2022 | Thunderstorms | 1,778 | 26% | 8.5 h | 8.5 h | 12k |
| Apr 17, 2025 | Winter storm | 1,779 | 26% | 14 h | 3.2 h | 7.2k |
| Nov 30, 2023 | No storm report | 187 | 3% | 7.2 h | – | 1.4k |
| Jun 13, 2025 | Thunderstorms | 103 | 2% | 9.5 h | – | 746 |
| Nov 13, 2025 | No storm report | 129 | 2% | 4.5 h | – | 550 |
| Jul 17, 2024 | No storm report | 99 | 1% | 4.5 h | – | 396 |
| Aug 6, 2021 | Wildfire | 82 | 1% | 5.8 h | – | 390 |
| Jun 11, 2025 | No storm report | 304 | 4% | 1.8 h | – | 359 |
| Jul 28, 2021 | Wildfire | 97 | 1% | 3.0 h | – | 291 |
| May 1, 2025 | No storm report | 96 | 1% | 2.8 h | – | 260 |
| Jun 15, 2021 | No storm report | 105 | 2% | 2.2 h | – | 236 |
| Jul 17, 2023 | No storm report | 104 | 2% | 2.2 h | – | 234 |
| Jan 14, 2021 | No storm report | 82 | 1% | 1.5 h | – | 123 |
| Sep 1, 2023 | No storm report | 104 | 2% | 48 min | – | 78 |
| Dec 17, 2020 | No storm report | 82 | 1% | 48 min | – | 62 |
| Jul 2, 2024 | No storm report | 99 | 1% | 30 min | – | 50 |
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 Big Horn from twelve hours before it began to its peak. Matching shows coincidence, not proof of cause.
- No storm on record 47%
- Thunderstorms 33%
- Winter storm 19%
- Wildfire 1.8%
Who keeps the lights on
Utilities serving Big Horn
As each utility reports to the Energy Information Administration for its whole Montana territory, not this county alone. Outage minutes include major storm days.
| Utility | Type | Outage min / yr | Excl. major storms | Outages / yr | Residential ¢/kWh | Customers |
|---|---|---|---|---|---|---|
| NorthWestern Energy LLC | Investor Owned | 125 | 117 | 1.10 | 14.4 | 334k |
| Tongue River Electric Coop Inc | MT | – | – | – | 14.1 | 56k |
| Big Horn County Elec Coop, Inc | MT | – | – | – | 11.9 | 38k |
| Yellowstone Valley Elec Co-op | Cooperative | – | – | – | 14.2 | 21k |
| Mid-Yellowstone Elec Coop, Inc | MT | 207 | 207 | 2.22 | 12.5 | 15k |
| Big Horn Rural Electric Co | WY | – | – | – | 17.1 | 258 |
| Powder River Energy Corp | Cooperative | – | – | – | 13.2 | 51 |
| WAPA-- Western Area Power Administration | Federal | – | – | – | – | – |
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.
Next door
Neighbouring counties
- Carbon 4.9 h
- Rosebud 3.1 h
- Big Horn, WY 3.0 h
- Sheridan, WY 2.5 h
- Yellowstone 2.4 h
- Big Horn (this county) 0.9 h
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 6,865 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 →