Im just seeing this now and do agree that putting the gauge in the middle is probably the best place to get an ambient reading. But if hes misting both sides of the tank the warm end will have higher humidity due to warm air holds more moisture. Even if the water bowl is on the cool side if its not being warmed enough to evaporate and go into the air its not going to make much of difference. I put my water bowls right in the middle of the enclosure, it doesn't get to hot but warms enough to help with humidity.