I use to be like the OP, I would have nothing to do all summer and wait for snowboarding. I now appreciate the summers in The Rockies, but still don't love them as much as winter. They go by faster if you have stuff to do and there's plenty of it around. Find something you like and you will find summers enjoyable.
I picked up mountain biking as a summer sport. There are lots of trails for me to ride. I also hike a lot with my dog. I was not much of a hiker until I got a little rat dog. He is a great trail trail dog and is very amusing to watch when he crosses streams. I love how he behaves off-leash in the wild. Hiking would be boring and lonely with out him.
I think regular skateboarding is very close to snowboarding. I skate a little too.
IT AINT EAZY BEIN STEEZY