I agree, happened to me once, never sticked to a rail like that -_-.
WHen it's really cold outside, it will become less sticky but from what i've figured out, watchout for dark color rails (brown-black) because even if its cold outside, if it's very sunny they will heat up and stick. If it's all dryed up it will stick a bit more than if it's a bit wet. Like someone said, test it with the ski in ur hand or by stepping on it if it's not too high