Just a couple of niggly things that I see in some comments that need to be pointed out and kept in mind. I'm not AC professional, but by reading comments I can tell that some folks don't have the whole picture.
An AC system continually moves heat from one location to another location. Efficient operation needs a compressor that works well (and has sufficient RPM to do so), the proper amount of refrigerant, and good heat shedding at the condenser. This comes in multiple forms - cool air, lots of air, both... Outside temperature and volume of air directly affect the system's ability to shed the heat it has removed from the cabin. You need a condenser that is clean of debris on the outside (and inside) and sufficient airflow through the outside. The higher the outdoor temperature (humidity doesn't really matter to the condenser end of the system) the more air you need to transfer heat. A perfectly working condenser will reduce the liquid refrigerant's temperature to the outdoor ambient temperature (it cannot do more). When you spray water on the condenser, you are adding the evaporation of that water to the cooling equation and you can cool below the ambient air temperature (like when a fan blows on you when you sweat), plus the cooling effect of the water itself. Testing this can help to determine if the limiting factor of the system's performance is the heat shedding half of the system.
The heat absorption happens at the evaporator, absorbing heat by changing the state of the refrigerant from liquid to gas, like continually spraying an aerosol can. I don't believe I've had a vehicle that did NOT have a TXV, meaning there is a valve at the evaporator with a closed feedback loop control that keeps the evaporator no lower than just above freezing so that it does not ice up. How energy is absorbed at the evaporator takes two forms - lowering the temperature of the air as it passes through and removing humidity (changing the state of water from vapour to liquid). The latter takes more energy than many people think. How much energy would it take on your stovetop to boil a pan of water dry? That same amount will be removed to condense that water back. If the interior of my house gets hot and muggy and I turn the AC on, it will run full out for an hour and the temperature won't hardly budge, but the humidity will drop 10% and it will feel much better (and water is pouring out the condensate drain).
How things work at the evaporator, assuming it is clean on the outside, is the volume of air (fan speed) and the temperature AND humidity of the inlet air changes the heat load offered to the system. This is dramatically different depending on climate and whether your system is running in recirculate mode or not. I see folks in this thread interchangeably comparing performance with recirc on and off - it is worlds different. If it's hot and muggy out, force the system to recirc and the system will work a lot less to keep the cabin comfortable. Your house doesn't stay cool by sucking in outside air directly - it recirculates the air that's in the house, cooling and drying it. It takes way more energy to start with outside air. Once you're past the hurdle of just getting into a hot car, reduce the fan speed and the discharge air will be colder and drier. Most vehicle systems don't actually recirc all the time - they let some outside air in periodically so you don't suffocate.
On a fully manual system on my first car, when I started doing this kind of thing, I was amazed how comfortable it could keep the interior set to recirc and low or low-med fan speed once the system had a chance to take the worst of the heat out of the interior.
