At least three people were hurt, The Seattle Times reported.
About 50 panicky people left their vehicles on the Highway 520 bridge as waves washed onto the span, causing it to sway and bounce, State Patrol Trooper Chris Webb said.
"It's been a crazy day,'' Webb told the newspaper.
"I've been on [the patrol] 22 years. I don't think I've ever seen something like this."
The bridge was closed for about 2 hours, reopening just after 1 p.m. PDT.
The newspaper said the injured included a construction worker hurt when a piece of metal awning he was installing blew off and hit him, a 2-year-old boy hit by a falling branch and a 48-year-old Granite Falls man seriously injured when a tree fell on his car.
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