Ferrell 18Z temperature 1981 - -15.8 -21.2 -34.2 -31.1 -28.9 -33.1 -36.7 -38.8 -29.2 -18.8 -9.4 1982 -8.9 -16.2 -31.5 -35.3 -35.8 -35.6 -39.9 -31.5 -36.7 -28.5 -16.9 -8.0 1983 -9.5 -20.3 -24.9 -23.4 -25.0 -37.6 -36.5 - - - - - 1984 -10.4 -17.0 -23.7 -25.2 -28.9 -30.8 -35.5 -36.9 -34.9 - - - 1985 - -19.1 -24.4 -31.4 -30.8 - -43.5 -37.4 -34.3 -27.1 - - 1986 - -16.1 -24.2 -28.5 -24.9 -31.4 -34.6 -40.5 -43.5 -27.4 -16.3 -9.3 1987 - -17.3 -28.3 -32.1 -29.8 -27.9 -32.9 -35.3 -30.9 -27.6 -19.0 -7.6 1988 -9.4 -16.6 -27.9 -27.6 -28.3 -28.3 -34.7 -24.5 -27.4 -21.6 -16.7 -7.7 1989 -7.8 -17.8 -23.4 -25.1 - - - - - -23.6 -14.1 -7.8 1990 -9.3 -17.8 -27.2 -28.1 -29.6 -34.7 -34.3 -38.4 -39.0 -29.1 -17.0 -8.6 1991 -10.6 -13.5 -27.9 -28.4 -32.6 -27.6 - - - - -16.5 -8.3 1992 -9.2 -17.8 -21.0 -33.4 -29.3 -33.4 -30.7 - - - - - 1993 - -15.6 -25.8 -27.4 -34.7 -28.7 -31.5 -37.5 -33.3 -30.2 -15.2 -9.6 1994 -9.2 -18.0 -29.8 -24.7 -35.5 -32.1 -32.6 -37.3 -39.5 -24.1 -14.8 -7.9 1995 -9.2 -15.0 -27.9 -34.8 -34.6 -30.0 -36.1 -33.4 -34.0 -27.8 -15.3 -6.7 1996 -7.7 -16.7 -28.7 -25.1 -31.2 -31.9 -35.2 -29.0 -32.4 -28.5 -15.4 -7.3 1997 -8.5 -18.2 -29.2 -34.1 -30.2 -29.3 -35.6 -40.4 -31.0 -20.7 -10.9 -6.7 1998 -9.1 -12.2 -24.9 -36.3 -29.2 -24.6 -35.3 - - - - - 1999 - -16.2 - - - - - - - - - - 2000 - - - - - - - - - - - - 2001 - -14.4 -28.5 -27.8 -32.3 -27.3 -29.3 -42.0 -32.3 -26.9 -15.9 -7.1 2002 -7.3 -16.1 -21.4 -28.7 -26.8 -35.1 -38.2 -37.7 -28.3 -22.4 -14.1 -8.0 2003 - - - - - - - - - - - - 2004 - - - - - - - - - - - - 2005 - - - - - - - - - - - - 2006 - - - - - - - - - - -14.4 -7.9 2007 -5.3 -13.8 -22.8 -28.2 -26.4 -28.1 -29.5 -30.1 -28.0 -27.0 -13.6 -6.2 2008 -6.1 -16.0 -22.3 -26.7 -29.7 -23.1 -34.0 -41.4 -25.0 -22.2 - - 2009 - - - - - - - - - - - -