A large raindrop (about the size of a housefly) is estimated to fall at about 20 miles-per-hour. Technically, this rate is expressed in meters-per-second in meteorological circles (20 mph = 9 m/s). This is not fast enough to cause you pain if you get hit on the head, but it is fast enough to cause soil erosion if there are enough of these raindrops falling at once.
At what speed does a raindrop fall?
Dateline article| David Murphy|