Hamilton County Power Outage History
2015–2025 · Iowa
Better than average — fewer or shorter outages than most counties. How grades are calculated
Outages by year
Outages by month (seasonality)
Worst outage events on record
| Date | Duration | Customers affected | Cause |
|---|---|---|---|
| Dec 16, 2021 | 9 hrs | 1,621 (17%) | Tornado |
| Apr 3, 2020 | 1 hrs | 1,431 (15%) | Unnamed event |
| Dec 10, 2021 | 16 hrs | 1,317 (14%) | Unnamed event |
| Aug 10, 2020 | 15 hrs | 1,142 (12%) | Drought |
| Aug 10, 2020 | 6 hrs | 1,123 (12%) | Drought |
Over the 11 years from 2015 to 2025, Hamilton County recorded 209 distinct power outage events, averaging 2.6 hours per event.
The single worst outage on record in Hamilton County started December 16, 2021 (Tornado), lasting 9 hours and leaving up to 1,621 customers without power (17% of the county) at its peak.
May has historically been the worst month for outages in Hamilton County, with 27 events recorded during that month across the dataset.
Based on this history, Hamilton County earns a Reliability Grade of B, placing it in the 80th percentile nationally for grid reliability (higher percentile = more reliable).
Sized for Hamilton County's outage profile
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Outage-prep kit
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Similar counties in Iowa
Counties with the closest reliability grade and national percentile to Hamilton County.
| County | Grade | National percentile |
|---|---|---|
| Cerro Gordo County | A | 80th |
| Clarke County | A | 80th |
| Clayton County | A | 80th |
| Decatur County | B | 79th |
| O'Brien County | B | 79th |
FAQ
How often does power go out in Hamilton County?
Between 2015 and 2025, Hamilton County recorded 209 outage events, averaging 2.6 hours each.
What is Hamilton County's reliability grade?
Hamilton County has a Reliability Grade of B, in the 80th national percentile.
What was the worst power outage in Hamilton County?
The worst outage on record started December 16, 2021 (Tornado), lasting 9 hours and affecting up to 1,621 customers.