Ignition won't turn over when moist

89 Cherokee, 4.0L, manual tranny, 4WD. When I attempt to start my Jeep after it has not been started for a while (especially when the air is moist) it won't turn over. When I finally do get it to respond there is 1 tiny spot in the key position where it will start. If I turn the key all the way to the end there is no response but when I turn the key back slowly it will finally catch in that one place only. Can anyone help me figure this out? Thanks in advance.

Your ignition switch sounds like its on its way out.