For hail, the dew point level is at a lower altitude than the freezing level. So water droplets form but have to be carried back up to freeze. They therefore occur in summer thunderstorms and other events that have a violent vertical air movement. Sometimes they go up and down between the dew point level and the freezing level building up successive layers of ice and gaining in size till they are too heavy to be carried back up. Hence the biggest hailstones are formed in massive tropical heat fuelled thunder clouds.
Snow forms when the dew point level is above the freezing level, so that moisture condenses as ice crystals (snow).