SPOKANE, Wash. — This time of the year in the Northwest often brings one thing to mind: Smoke. There are a few reasons why the smoke hits the region so hard.

The Northwest region sits between the Cascades and the Rockies. Usually, this would help shield the area from any extreme weather. However, when smoke fills the area, it can settle in lower valleys and stays stagnant.

Without rain, strong wind, or any significant weather event, smoke can act like dry ice does in a bowl. It sits still until another force moves it out.

The smoke in the air Tuesday is from the Williams Flats Fire burning over 16,000 acres on the Colville Reservation in Ferry County.

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