Why the rain was so dirty this week

Many of you have written in asking what this dirty rain from Thursday was all about. It left many vehicles completely covered in a brown powder that at times resembled pollen. It was actually dust from the desert southwest!

It may sound crazy, but those dirt particles that are sitting on top of your vehicles are from New Mexico and Texas! They literally traveled a thousand miles and ended up here in the Quad Cities thanks to the intense area of low pressure that formed and moved through our region. How does this process work?

Satellite imagery from Wednesday shows quite clearly how this dust became part of the equation. Strong winds driving into the area of low pressure picked up the dust from the southwest and then drove it northward. The dust actually serves as an important tool for rain formation, believe it or not.

Before rain clouds can form, the moisture in the air needs a catalyst (or a carrier) to move upward in our atmosphere to condensate (or form a cloud). Frequently, dust and other particles in our air act as these carrier mechanisms to get the whole process started. So, the dust particles that are sitting in our cars and trucks played quite the role in creating the rain that fell here this past Thursday.

If you are looking for a good car wash day, I would do that on Saturday. Windy conditions today will continue to drive some pollen into the air, and that will likely mess up your clean car should you choose to wash. By Saturday, the winds will be lighter and temperatures will also be warming back into the 50s, making things a bit more comfortable to do some extra detailing. The next chance for any significant rainfall will hold off until Sunday.

Meteorologist Andrew Stutzke

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