If a player is within the aoe of their own cold snap spell, they will be slowed or damaged and frozen as well. Not sure if this is a bug, but if it isn't it makes cold snap kinda useless in close quarters. Flare is a very similar spell, but since it doesn't ignite the caster and thus doesn't do damage to you unless you're already on fire, it's superior to cold snap in almost every situation, so cold snap being like this doesn't make sense. The only time cold snap as it is makes sense to use is with a bow, since you usually won't be close to your target.