My understanding is that sleet is frozen in the clouds and falls in the same form. Lots of "rain" starts off frozen, then when it reaches warm enough air, it becomes rain. Hale is formed first as sleet-size droplets, falls some through rain and that rain sticks to the sleet over and over again, until it is hail. Needless to say, since I am not in a winter-weather ice region, I don't have much experience and certainly not much knowledge how this stuff works.
