I have left my batteries and airplanes outside in my trailer all winter, for the last number of years. We regularly get -40' for extended periods of time....thats not a typo....In the fall before winter, I fully charge my Nixx packs and LiFe packs, and Lipo's into storage charge. Last winter a switch got bumped on and a LiFe pack was drained, and was froze for months, and it recovered fine!