I noticed after the heavy rains on Sunday/Monday, my car was dirtier than it was before it rained. It went from having dust on the sides to thick dust in spots all over. I saw other cars with the same issue.
Today I stumbled across a weather blog that said a dust storm in the plains hooked up with the front that came through Sunday into Monday, causing the dust to be absorbed by the rain, thus causing it to be deposited during the storm.
Thought it was interesting. Here is a video of the storm and fires in Texas that caused it.
