This was not planned to leave the tumbler in the car over night, but I forget it and was not thinking I wanted my ice tea until the next day. I was very happy to see it was still cold inside and had a few pieces of ice left in it. I figured it was about 8-9 hours in very hot and humid weather with the windows closed, but during the night. This tumbler does not have a handle but that is ok, I am able to grip it easily. And if I need a handle I will just use one form another mug.