I'm so pleased I came across this post, as this is one of the things I'm concerned about when we do get our guinea pigs. How cold is considered too cold to be left outside in a hutch? Unfortunately we don't have the space to put up a shed for them to go in, nor is there enough space in our garage. I have ordered a thermal cover for the hutch and a microwaveable heat pad, but I do worry it will still not be enough. We have also bought an indoor cage to use for the cold weather, but could it confuse the guinea pigs if they are changed from one living space to another?