I have decided we need a:
No hats, but shades and bikinis.
I don't see why we need this. Of course, it will be fun (at least, most users see it that way).
Winterbash was introduced to mitigate the lower visitor counts during the winter holiday season. This idea worked out well, but only has a limited use. I don't see why we would need a Summerbash (or anything like it):