Things to do over the summer? (Underage college student)

I go to university in California but I'm here for the summer. I'm originally from Reno so I'm familiar with the area, but I'm still curious how other college-aged people spend their time here, and if there's anything new or interesting that I don't know about. Sadly I have nothing in common with my old hs friends here so that's a bummer, but I'm trying to make the most of it! And I'm only 20 so no bars or beer crawls for me.

I'm genuinely curious: What do other college kids do in the summertime besides the usual Tahoe trip? Should I just start volunteering or something? (And where can I meet other people my age hahah)