Originally Posted by Electrix
I'm thinking it's something to do with her past. Storm is the only character we know nothing about before X1. Everyone else has either appeared in flashbacks (Jean in X3), spin-off's (Cyclops in Origins) or had their backstory fleshed out in First Class.
Storm was in Wolverine: Origins
In novelization of the first X-men movie were scenes with young Storm. She was bullied by children and her powers manifested, her hair turned white and she created snow and ice storm, and attacked children. As i remember Xavier found her at that moment