The hair definitely keeps them warm in the cold and cool in the heat. We live in Orlando and when I worked a pet fair back in September for Pyr rescue, we took all 3 dogs. Cody, my TM, Jake, my Pyr and Max, my IW. Cody spent the entire day laying under the tent, out in the heat and was just fine, no excessive panting, nothing. Jake was okay for a few hours and then started the panting and non-stop drooling. Max was dying after about an hour and I sent him home. They all live in my house in AC constantly, however, Max just can't deal with heat at all. We have to crank the vehicles and cool them down if we want to take him anywhere in summer. Jake does much better with heat than Max does. He still wants to run on our walks no matter what the temp is. I brush him twice a week and never trim him.