Sleet is frozen rain that goes "splat" when it hits the ground or other things that might be in its path. Sleet is usually about the size of rain drops. Moisture collects and falls out of the clouds. On its way down, if the temperature is right, the moisture will freeze and fall to the ground as sleet. Hail is big frozen drops of rain made during wild thunderstorms. Hail falls from the sky and then the wind picks it up and carries it back into the cloud. Then it falls again and collects more water which freezes. This process is repeated until it gets too big and heavy for the wind to carry it back up to the cloud. Then falls to the ground as hail. Sometimes the hail is big as baseballs, while other times they are small as peas.