Meteorologist Karl Loeper, National Weather Service, Allentown, reported today that December 1989 is in the books as the coldest December since 1912 when weather record-keeping began in Allentown. The month averaged a bone-chilling 21.2 degrees - 10.3 degrees below normal - and three degrees lower than the record cold December of 1960. Loeper predicted that there is a 60 percent probability the average temperature in January will be below the normal of 27.2 degrees. The warmes January on record was 1932, when the average was 40.6 degrees.