I live in Phoenix. When I first moved here, I lived in a shitty apartment that didn’t maintain my air conditioning, and the condenser drain clogged and started leaking, so I had to put out buckets to catch the water. I could easily squeeze a gallon out of the air in a few hours, and that was just a 750 sqft apartment…

“relative humidity” is the percentage of water the air holds relative to how much it could hold, which varies by temperature. It can’t go negative, though it can go over 100%.