Wait, most universities don't offer summer classes? Where I went to school there were fewer students enrolled over the summer, but that just meant campus was a bit less crowded, not that it was a ghost town.
I would have gladly attended 90% of my classes in the summer had they been offered to students. Especially, those mid-tier classes that are only offered in Spring or Fall. IE: intro1 (Fa, Sp, Sum1, Sum2) -> intro2 (Fa, Sp, Sum1, Sum2) -> mid-tier class (Spring only) -> opens up 10 classes.