We've just had our first taste of fall with early morning temperatures in the 40s. Since I do see some differences in patterns with lower temperatures and higher humidity, I plan to get out early soon to pattern shells some while those temperatures are down. In that way I'll be ready for the fall season and also know just how my gun will pattern on those cool spring mornings next year.
If you've not patterned your gun on a cool and damp morning, it's something that you might want to try just to see if your patterns are effected.
I also allow enough time for my gun and my shells to become cool/cold to the touch, just like when I'm out hunting. I want to be as close to actual hunting conditions as possible. A cold gun, cold ammo and cold atmospheric conditions can make a difference in performance of our equipment.
Might be worth a try.