I'm from central FL and have used my JoyeTech & eGo batteries with clearos & tanks, mods with tanks, etc. anything & everything in our summer FL sun with no problem. Use them while mowing my pastures for hours April-October, and catching some rays at the beach for the day mid-May through September...never a problem at all. At the beach, I just make sure it's not left out on my towel or something when I'm swimming. It's always covered up with my towel & in the shade of an umbrella then. I also never, ever, leave them in my car, especially in summer.