The tornado hit Seattle's industrial area of Frederickson at around 7:20 a.m. where it tore a hole in the roof of the Northwest Door Factory, blew out car windows at nearby Boeing factory, and damaged a building where sections of a downtown Seattle tunnel project were being assembled.
No injuries were reported at either of the scenes.
A team from the National Weather Service office in Seattle confirmed the tornado from the scene based on eyewitness accounts, meteorologist Johnny Burg said.
The Weather Service classified the tornado as an EF1, with a maximum wind speed of 110 mph.
"It looked from the inside like a wave going along. You could actually see the roof flexing," Northwest Door President Jeff Hohman said.
According to Weather.com, parts of the Northwest got more rain over the weekend than typically falls in the entire month. The site claims this has been the wettest September on record in Seattle and Olympia, Wash., and in Portland, Ore.
Additionally, The storm brought along the first significant snow of the season to the mountains.
"We basically had conditions well off shore that were very reminiscent of late fall-early winter," said Dana Felton, a meteorologist at the Weather Service office in Seattle.