If you're looking for a fun and inexpensive way to cool off this summer but still want to enjoy something outdoors, Wake Island Waterpark is probably your best bet.
The park is just north of Sacramento in Pleasant Grove, and you can enjoy wakeboarding, a floating obstacle course, human hamster wheels, ninja race course, paddle boarding, and ziplining for pretty affordable prices. This isn't an ad - I'm just saying I think the cost is WELL worth it.
Entry is free, but if you want to partake in any of those activities (seriously, who doesn't??), they have several different season pass and rental options. Also, they have cabana rentals!!! How fun is that??
If this is something you definitely want to check out this summer, they do require online booking so keep that in mind. Check out their website here, and take a look at their Instagram for photos and updates at the park.