Used to love the 6" rain in Tucson--usually just after you clean the car of course.
BIG raindrops 6" apart and then the dust from the edge of the storm blows by and sticks to the water drops. You end up with abrasive little mud balls all over the car.
Actually saw 1" mud balls falling like soft hail when I was in New Mexico--now that is a trip when it rains thru the dust storm.