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Washington Thanksgiving Travel: Even Treated I-90 Can Freeze
Seattle, WA – Washington drivers preparing for Thanksgiving travel along Interstate 90 should know that even a freshly treated highway can remain dangerously icy. From the Seattle metropolitan area to
By Lauren Beckett · 2026-11-11T19:36:25.574Z
Seattle, WA – Washington drivers preparing for Thanksgiving travel along Interstate 90 should know that even a freshly treated highway can remain dangerously icy. From the Seattle metropolitan area to Snoqualmie Pass and eastern Washington, freezing pavement, mountain snow and rapidly changing weather can create hazardous conditions despite winter maintenance efforts.
According to winter maintenance guidance from transportation agencies, conventional road salt becomes less effective as pavement temperatures approach 20 degrees Fahrenheit. Its ice melting ability declines further in the teens and single digits, although performance depends on the treatment used and roadway conditions.
Why Treated Washington Highways Can Still Freeze Salt and other deicing materials help prevent or remove ice, but they cannot guarantee traction.
Around 20 degrees, conventional salt works more slowly than it does near freezing. Below approximately 15 degrees, salt alone may struggle to melt ice quickly enough to improve road conditions.
That matters along I 90 through Bellevue in King County, Ellensburg in Kittitas County, Moses Lake in Grant County and Spokane in Spokane County.
Snoqualmie Pass, east of Seattle, presents additional hazards because mountain snowfall, wind and freezing pavement can affect traffic even after snowplows and treatment trucks have passed.
Other major corridors, including I 5, I 82 and I 405, can also become slippery during winter weather.
Thanksgiving Travel Could Increase the Danger Thanksgiving falls Thursday, Nov. 26, bringing holiday traffic onto Washington highways connecting Seattle, Tacoma, Everett, Spokane and communities east of the Cascades.
If snow, freezing rain or rapidly falling temperatures develop during the holiday travel period, treated roads could remain dangerously slick.
Mountain passes deserve particular attention because conditions can change sharply with elevation. Drivers may also encounter traction or chain requirements during winter storms.
The Washington State Department of Transportation uses plowing and winter maintenance treatments, but no method guarantees ice free pavement.
Before departing, motorists should check National Weather Service forecasts and WSDOT's real time travel information for highway conditions, mountain pass restrictions, closures and traffic cameras.
The bottom line: Treated does not mean safe. Reduce speed, increase following distances and prepare for rapidly changing conditions, especially when crossing the Cascades.