Being in Minnesota, theres always enough snow to go around. Snowball battles occured pretty often after church or activities among the youth, so I took it and changed the rules abit.
First, you split the the group into medium size groups (3-7). Then you give them 5-10 mins to build up a snow man at a given height (your call). After the ten minutes, you tell the group that their goal is to knock down or apart any of the other teams snowmen using only snowballs. The first team to do this wins! Its not only safe but fun and CRAZY!! You can have defenders if you like, hold the games in huge fields with the teams spread apart or even give a time limit. Snow is wonderful, aint it?!