.2 and 2 mph comparing typical summer to decent fall. Can be more with extremes. But I dont chase the weather with my tune.

A few years ago I ran on back to back fall weekends at T&T only at PRP (at that time). I always have my weather meter out and guys like to chat about it. The first weekend day was nice and my weather station said it was very good air. The second weekend day seemed very much like the first one, but the pressure was actually a bunch lower. My car pretty much hit the numbers I calculated base on the different DA. A bunch of guys came looking for me after there first pass as they were all a couple tenths off on what seemed like the same conditions. They were happy, but a bit surprised that it was the atmospheric conditions for what seemed like similar days.