The Key to Summer is the title of the 89th issue of the Italian comics series W.I.T.C.H.
Thanks to Taranee's parents, the girls get a summer vacation in Sleepy Bay. They see this as an oppertunity to practice their new weapons. When Will tries to find the lock for the key they got from Yan Lin, she gets herself into trouble and the girls end up being chased away from the Cobalt Blue concert. Then, when they least expect it, they find the lock to the key... their new school is inside of a magical bus!