When the air is humid, your cold drink sweats more. What you are seeing on your glass or can is condensation.  When condensation happens, your drink warms up. Here's the process: there is water vapor in the air. It's in gaseous form, so you don't see it.  That water vapor changes to its liquid phase through a process called condensation. The water vapor "loses energy" in this process which releases heat into the environment.  That's what warms your beverage! 

Recent research suggests your drink will sweat twice as much in high humidity as in a "dry heat."  We reached a maximum dewpoint this afternoon in the middle 70s!! That's MISERABLE, and it heated up your drink by several degrees in just a few minutes. The solution: a koozie or some sort of wrap for your can/glass.  Not only does it insulate your drink but it stops condensation from forming on the outside. 

-Hannah Strong