Every car I've ever owned did this to some extent. Check to see that the fan is running....it should run any time the compressor is cycling. Check for a dirty / obstructed condensor. Pressure wash any dirt / bugs off it. If it can't shed heat well, the system won't cool properly. If it persists, have the system pressure checked. It might need freon, or could possibly have the wrong ratio of freon / refrigerant oil. Too much refrigerant oil will cause ineffective cooling.