Massive Power Outage Affects Over 94,000 in Wyoming, South Dakota

News – Sheridan Media

A massive power outage that affected approximately 95,000 customers in Wyoming and South Dakota Thursday is believed to be the result of two tripped 500-kilovolt transmission lines near Medicine Bow according to Western Area Power Administration Public Affairs Specialist Stephen Collier. The tripped lines caused an unusual voltage event that set off a cascade of other tripped lines resulting in the rolling power outages throughout the Cowboy State and western South Dakota.

Areas in Wyoming affected by the outage Thursday included, but were not limited to, Sheridan, Buffalo, Gillette, Newcastle, Glenrock, and Casper. The county-wide outage in Sheridan County prompted emergency management officials to open the Sheridan County Fairgrounds Exhibit hall as a temporary warming center and shelter for those without power.

There was also a fire Thursday at the Dave Johnston coal-fired power plant near Glenrock. Wyoming Department of Homeland Security Director Lynn Budd said the fire at the power plant occurred after the outages began. It is uncertain at this time if the outages caused the fire at the power plant.

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Last modified: November 14, 2025