Will it stay clingy in the summer heat?

My clings look great, just like the artwork I uploaded. But the clingy-ness seems to be stronger on the back of the sticker rather than the front. When I put a sticker on the inside of my glass windshield, it peeled off in the sunshine within an hour and was sitting on the dashboard. I have re-applied it to try again, it hasn't fallen off, but it also hasn't been a warm, sunshine-filled summer day in the South yet! I'll be curious to see if this cling sticks.