Boise County, Idaho – Idaho Highway 21 closed between Lowman and Stanley due to avalanche risk, triggering travel disruptions.
According to the Idaho Transportation Department and Idaho State Police, the highway shut down at 1 p.m. Tuesday between Grandjean and Banner Summit because of a rising avalanche hazard.
Officials said crews are continuing to monitor snowpack and slope conditions in the area. The closure affects a key mountain corridor that connects Boise County and Custer County, particularly near Banner Summit.
Drivers are being directed to check 511.idaho.gov for real-time updates before traveling through the region. No timeline was immediately provided for when the highway may reopen.
The affected stretch of SH-21 is frequently used by commuters, commercial drivers, and recreation travelers heading to Stanley and nearby backcountry areas. The closure may require significant detours for those planning cross-mountain travel.
Transportation officials emphasized that safety concerns prompted the shutdown as avalanche conditions can shift rapidly, especially during periods of unstable snow accumulation.
Motorists are advised to avoid the area until conditions improve and the roadway is deemed safe for travel.
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