Snowballs are snow covered cropsies which cannot be distinguished. They cannot be matched, either. If a match takes place close to a snowball then the snow will be removed and unveil a regular cropsie. There are cold squares which convert cropsies into snowballs. With the help of seeds cold squares can be converted into grass. Shovels will uncover snowballs. Levels with snowballs tend to get stuck often because the snow is covering all moveable cropsies. Shuffling makes the situation even worse because some of the remaining Cropsies will be put on cold patches and be converted into even more snowballs.
Snow acts as grass for adult mushrooms. Standing on this environment, the value of a mushroom is increased by 2.