Power outage history
Sweet Grass County Montana
7.1hours
without power for the average customer in a typical year, 2018–2025
16th most of 35 in Montana close to 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 Sweet Grass's customers who were without power at that day's worst moment.
Year by year
Hours in the dark, per customer
2025 was the worst well-recorded year, at 11 hours for the average customer. Hatched years have a thin record and are left out of the averages.
Sweet Grass, 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 |
|---|---|---|---|---|---|---|
| Dec 17, 2025 | No storm report | 1,612 | 81% | 30 h | 24 h | 12k |
| Oct 26, 2021 | No storm report | 1,314 | 66% | 4.8 h | 4.8 h | 6.2k |
| Dec 9, 2025 | Winter storm | 817 | 41% | 16 h | 3.2 h | 3.2k |
| Jan 13, 2021 | Windstorm | 331 | 17% | 12 h | 7.2 h | 2.7k |
| Feb 2, 2020 | Winter storm | 285 | 14% | 9.5 h | 9.2 h | 2.6k |
| Sep 21, 2023 | No storm report | 297 | 15% | 8.5 h | 8.5 h | 2.5k |
| Apr 17, 2025 | Winter storm | 513 | 26% | 5.0 h | 3.8 h | 2.2k |
| Aug 3, 2020 | No storm report | 206 | 10% | 9.5 h | 8.0 h | 1.7k |
| Jul 22, 2020 | No storm report | 575 | 29% | 4.0 h | 3.8 h | 1.7k |
| Aug 6, 2020 | No storm report | 575 | 29% | 3.8 h | 3.8 h | 1.4k |
| Jan 22, 2023 | No storm report | 292 | 15% | 4.8 h | 4.8 h | 1.4k |
| Mar 12, 2022 | Windstorm | 290 | 15% | 4.8 h | 10 h | 1.4k |
| Feb 10, 2022 | Windstorm | 222 | 11% | 6.0 h | 6.0 h | 1.3k |
| Jul 28, 2021 | Wildfire | 288 | 14% | 6.2 h | 6.2 h | 1.2k |
| Jul 4, 2020 | No storm report | 323 | 16% | 3.8 h | 3.8 h | 1.2k |
| Nov 19, 2023 | No storm report | 261 | 13% | 4.5 h | 4.5 h | 1.2k |
| Jun 10, 2022 | No storm report | 293 | 15% | 4.0 h | 4.0 h | 1.2k |
| Sep 13, 2022 | No storm report | 85 | 4% | 13 h | – | 1.1k |
| May 23, 2024 | Winter storm | 351 | 18% | 5.0 h | 13 h | 1.1k |
| Aug 12, 2024 | No storm report | 522 | 26% | 3.2 h | 1.2 h | 1.0k |
| Jul 18, 2022 | No storm report | 292 | 15% | 4.2 h | 4.2 h | 1.0k |
| Aug 7, 2024 | No storm report | 230 | 12% | 4.5 h | 4.5 h | 1.0k |
| Jun 2, 2025 | No storm report | 230 | 12% | 4.0 h | 4.0 h | 920 |
| Mar 9, 2021 | No storm report | 608 | 31% | 2.0 h | 2.0 h | 912 |
| Sep 8, 2023 | No storm report | 295 | 15% | 3.0 h | 3.0 h | 885 |
| Jul 24, 2023 | No storm report | 200 | 10% | 4.5 h | 1.0 h | 872 |
| Mar 11, 2022 | No storm report | 225 | 11% | 5.5 h | 6.5 h | 868 |
| Oct 1, 2023 | No storm report | 297 | 15% | 2.8 h | 2.8 h | 817 |
| Oct 4, 2024 | No storm report | 57 | 3% | 17 h | – | 801 |
| Apr 15, 2024 | No storm report | 411 | 21% | 2.5 h | 2.2 h | 778 |
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 Sweet Grass from twelve hours before it began to its peak. Matching shows coincidence, not proof of cause.
- No storm on record 72%
- Winter storm 13%
- Windstorm 11%
- Wildfire 2.6%
- Thunderstorms 1.3%
Who keeps the lights on
Utilities serving Sweet Grass
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 |
| Park Electric Coop Inc | MT | – | – | – | 9.6 | 81k |
| Beartooth Electric Coop, Inc | MT | – | – | – | 13.1 | 51k |
| Fergus Electric Coop, Inc | Cooperative | 480 | 284 | 3.03 | 15.9 | 6.9k |
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
- Meagher 33 h
- Wheatland 20 h
- Golden Valley 13 h
- Sweet Grass (this county) 7.1 h
- Park 5.3 h
- Stillwater 2.0 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 1,993 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 →