Lucky Boise residents made it through the howling winds that swept through Idaho on Sunday night and Monday morning with little to no damage. But many in the Treasure Valley still need to stop by a car wash soon or get a power washer for their home’s windows.

So just what is that dirty film all over vehicles and glass, and how and why is it seemingly everywhere?

According to Josh Smith, a meteorologist for the National Weather Service in Boise, this type of “dirty rain” descended on the Treasure Valley after cold-front winds kicked up dirt and dust as far away as central Oregon and then flew it eastward.

That wind, coupled with the slightest amount of rain Monday, created the film of filth seen by many in Boise and its surroundings. Smith said this sort of dirty rain, when it does occur, is most typical in the spring months.

What is atypical, Smith said, was the time at which the wind gusts occurred. Stronger gusts more commonly take place during the day, when there are warmer temperatures and more wind movement at the ground level.

“We don’t typically see wind gusts around 60 or 70 miles per hour that late at night,” Smith said.

He added that much of Idaho experienced the strong wind, which is also unusual. The storm featured gusts of up to 60 mph in McCall, for instance, an area that seldom sees such wind, according to Smith.

Many areas of Southern and Southwest Idaho were under wind advisories and warnings Monday afternoon as well, as gusts continue throughout the day.

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