Nothing to do in Grand Rapids in April

So I have a friend visiting the last two weeks of April. He asked if there were any cool events or other things going on in Grand Rapids... After looking around and checking things out.. the short answer was no! I think April is a hard time for indoor and outdoor events. It's not quite warm enough to do stuff outside, yet it's warm enough everyone wants to be outside. No big events downtown yet... but people still want to be outside.  I told him to Come back in June!    What's happening in GR in April anyway?