I would say there was a problem with your air conditioning system.
It should first be determined whether your A/C compressor is attempting to turn on, or if nothing is happening at all. To do this, sit with the a/c button selected for a period of time. If you here a click every once in a while & the rpms lower for short periods of time with this click, your a/c compressor clutch is probably attempting to engauge, but is stuck. Go out and check it under the hood. If it just locks & your belt slips over it, this is the problem.
The next possibility is that you do not have enough freon in your system. When this happens, the car will not even attempt to engauge the a/c compressor. Look for one of the freon refill valves under your car (like the one behind passenger headlight) and press it very quickly to check for releasing gases. If nothing comes out or only a little is released, you could be low on freon.
The first problem would be the easier one to diagnose. Other problems could also exist, but I believe these are more common.