key won't go into ignition slot

The same thing happened to me in WI, it's been really cold and I don't know what is wrong but it is like I am using the wrong key! Does it have to do with the cold weather?

try spraying alittle wd-40 in key slot works for us and i have1971! i allso make a habit of getting some really good grease and put on door jams ,hoods any thing that opens and closes like behind door panel depending on what model you have