When we were kids we used to catch pike all year (Most of the time when we weren't fishing for them ).
I know that a lot of people fish for them in the winter rather than the summer, but I think this is more because they still stay active compared to a lot of other species during the colder months rather than it not being right to fish for them in the warmer months (Of course; I don't claim to be an experienced pike fisherman at all, so could be woefully wrong )