I thought it was interesting that the Barometric pressure followed the same curve as the Humidity. I was looking on the internet and it says that the air is lighter when the air is humid. Looking at these two graphs that is not the case. I'm beginning to think that when the air has water in it, that causes the air to become heavier, thus increasing the pressure. I'll have to observe this over several days to see whether or not answers.com is wrong.