Inversely to the heat. What I mean is, while it does make some noise (mild, easily spoken through, and not distracting at any speed), the hotter it is the less it matters. I was using this in a dry climate, where temps ranged from the mid 90's to mid 100's. The hotter it got the less I cared about noise, if I used it when I was trying to sack out a bit through the heat, inside my tent. But... that I could nap with it should give some clue too, I had sort of forgotten about that part.