Snoqualmie Pass - Weather

Weather

Snoqualmie Pass as it climbs into the Cascades passes through a micro-climate characterized by considerable precipitation, and at times hazardous conditions for travelers. The annual rainfall is over 100 inches per year, snowfall is over 400 inches per year. The number of days with any measurable precipitation is 170 or more per year.

The rapidly changing conditions require special cautions, relayed to motorists via variable message displays along I-90. Depending on traction they may call for tire chains to be installed, usually on large trucks but occasionally on smaller vehicles as well. Chain-up areas are provided along the side of the Interstate to facilitate the placement of chains. The pass has been subjected to closures when weather conditions become extreme.

Along one stretch of I-90 is a snow shed over the west-bound lanes, constructed in 1950 (47°21′20.68″N 121°21′57.65″W / 47.3557444°N 121.3660139°W / 47.3557444; -121.3660139 (snowshed)) for US 10. The use of sheds (very rare on Interstates) is an admission that plowing cannot keep up with snowfall and avalanches. A recent proposal suggests replacing the shed with a bridge to allow snow to pass under the highway.

WSDOT maintains cameras at selected locations along the pass to monitor weather conditions. Some of these cameras can be viewed via the internet.

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