Interesting question Acid -
First of all you said harder thank we think when it comes to the weather. Are you playing poker outside? Or are you referring to the whether the air conditioner is running in a particular poker room?
I feel like a poker face comes from experience. I have been playing live poker for about ten years and it started when I was 18 or 20 in Indian Casinos. At first when I would hit a big hand or win a pot i would show a lot of emotion. I used to peer intently at the flop and then at opponents. Ive since practiced even how I reach for my chips. The key to me is establishing a pattern. The reason for this is consistency. If youre holding your chips in the same position, reaching with the same hand, and blank staring your opponents consistently - the only real worry you need to think about is your specific betting patterns. And by that I just mean sizing your bets correctly and consistently - or changing it in order to throw of your opponents.
To me im very robotic when I play now. I dont reach for chips or even hold my cards to fold until the action is on me. I peer intently at whichever opponent I think is going to give me the most trouble. The flop and other opponents from then on are just glances. I never look at my cards twice after being dealt. Its one and done.
Hope that provides some insight
Have a great day and best of luck at the tables -
Travis
BCP - horseshoebhole