('05 3S) A/C started blowing warm mid-drive
 

(2005 3s 5-door, A/T)

Driving back from the beach yesterday, with 4 friends in the car on a hot and sunny day, the A/C was turned on full tilt and seemed to be working normally. After about a half-hour of driving, we noticed that the air coming out of the vents was suddenly warm, as though the A/C had stopped working. The A/C console button light stayed lit, and turning the A/C off then on again didn't fix it.

I briefly drove the car today, and A/C appeared to be working again.

Any thoughts on what might have happened? Things I should check up on?