Yeah, humidity sucks in feeling but is better for your cooler than dry heat because of the water grains in the air.
Yes, I am assuming too that if you are building a water cooled set-up, you are going to upgrade to a larger resevoir. yes, mine is ridiculous (16 gallons) and is why I am working on a freon system right now but even a standard upgrade (vortech size) is going to do a lot better in DD conditions in the southwest type conditions.
The south, east coast, north and mid west, have a different kind of humid air and are a different animal. Again, I'm not saying air to air doesn't work in southwest conditions, I'm just saying a water cooled system is better under DD conditions for making power out here.
When we have 102º weather - it's dry heat and hot air you are trying to use. Your water temp in your resevoir is not 102º and should be around 90-92º on that day.
When you are in Louisana and it 'feels' like a 102º because the temp is 89º with a shit load of humidity, you are dealing with a lot of water grains in that 89º temp that the motor is utilizing in the air transfer.