In the hot summer heat and in the cold winter air, this bottle can handle it all. The insulation really helps to keep the water inside cooler than normal in the heat. I used many of these bottles during the Badwater 135 mile ultramarathon, and in the 125 degree heat, the water inside still remained cool. I also like the insulation in the cold weather, for the liquid inside does not freeze, and your hand does not get extremely cold when carrying it. These bottles are highly recommended.
Kathy, Wasatch Speed Goat Mountain Racing Team member