Driving 270 near Westport - Maryland Heights

Just wondering if anyone else has experienced this: in the last two weeks while driving to and from work (both north and southbound 270), I’ll randomly get a sprinkle of something on the car. The first time it was evening and I thought it was rain, except it sounded harder than rain, like sleet? I saw drops hit the windshield. Then it was over. 🤷🏻‍♀️The next day I noticed that the droplets on my car windshield were still there and appeared milky white. I thought random and odd, but there were no trucks around me that these drops could have been coming from. The next time it happened, it was late morning. Same thing, quick spray of droplets, milky white. Sounded loud hitting my windshield. No trucks. This was right around Westport. Where is it coming from??