Catch/get/grab some rays
Definition 1 of 1
Pro Tip 1/3Casual Expression
Used in informal settings among friends or in casual conversation. 
It's such a nice day, I might just get some rays at the park.
Pro Tip 2/3Weather Dependent
Only used when it's sunny or when the weather allows for sunbathing. 
The weather's great, let's grab some rays!
Pro Tip 3/3Summer Activity
Commonly associated with activities during the summer or in sunny vacation spots. 
I'm on holiday in Hawaii, planning to catch some rays every day!