pull the boot off of your shifter and then take off the lower boot, pull the bolt holding your shifter in and pull it out looking for water and or dirt and a bad lower boot, check your shift sheet(plastic thingy)make sure it is not worn thin, if not grease it real good with some molly type grease and put it back together, how cold is cold? it's 15 deg. here.  also pull the spring loaded detents in the shift tower apart and grease then real good.