AC stopped blowing cold air right in the middle of traffic

I was sitting in rush hour yesterday and suddenly my AC just started blowing warm air out of nowhere. No weird noises, no warning, just warm air. I pulled over and checked what I could but everything looked normal under the hood. I have no idea if it is a refrigerant leak or something worse with the compressor. I tried adding one of those recharge cans from the auto parts store last night but it did not seem to help at all. I think I need to stop guessing and actually learn more about how these systems work before I waste money on temporary fixes. It is frustrating because I rely on my car for work and driving around without AC in this heat is miserable. I might have to find a shop that really knows what they are doing with AC repairs.