In cold weather it always best to keep your guitar/bass away from the outside walls of your house when it is in it’s case or on a guitar stand. The cold air (plus the warm air inside your house) can affect your action (how high the strings are from the neck) and make your guitar harder to play.

Also…an article from the owner of Taylor Guitars on what you should consider when deciding on leaving your guitar out versus keeping it in the case.

http://www.premierguitar.com/Magazine/Issue/2009/Mar/How_Humidity_Affects_Your_Guitar.aspx