Residents in the St. Louis area woke up to dust and particles covering their cars. While some thought it was pollen, others were just confused by what caused the spots. 

What You Need To Know

  • Gusty winds from the Desert Southwest transported dust into the atmosphere late Thursday

  • Raindrops and dust particles combined, producing a “dirty” or “muddy” rain as droplets fell Friday morning

  • These raindrops collected and were visible on surfaces such as car windshields or hoods

Turns out, it was "dirty rain." 

What is "dirty rain"?

"Dirty” or “muddy” rain is just what it sounds like, rain that has dirt or dust particles in it. Dust can become suspended in the atmosphere and attach itself to water droplets. As these water droplets rain out from the cloud, the water and combined dust/dirt fall out with it.

It might not be noticeable on a surface that already contains dust or dirt on it, but the hood of a recently washed car would certainly show it. 

Desert southwest dust was transported to Missouri

Areas along the desert southwest saw windy conditions on Thursday. Thanks to drought conditions, the dust from this region was lifted into the air, creating low visibilities. Parts of Interstate-10 were shut down in Las Cruces, N.M. because of poor visibilities from the blowing dust. 

The particles were blown into the middle part of the country where they combined with the light rain we experienced this morning, thus producing the “dirty” or “muddy” rain. 

Our team of meteorologists dives deep into the science of weather and breaks down timely weather data and information. To view more weather and climate stories, check out our weather blogs section.