User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-4902593-20130225075602/@comment-16219425-20130225180624

Only Boreas kids (or his children's kids) can control ice and snow. But still, Percy may have LIMITED control over ice (maybe turn ice into water so he can manipulate it?). But still, if he can, he probably hasn't tested it. It's like saying if Leo can control lava, maybe but probably not.