Schwerdtfeger 18Z temperature 1985 - -21.5 -26.3 -34.1 -34.2 -35.2 -46.9 -39.4 -36.3 -28.7 -18.8 -8.8 1986 -9.0 -17.3 -27.1 -30.4 -27.2 -36.1 -38.3 -41.5 -45.0 -29.7 -18.0 -8.8 1987 -7.0 -19.0 -34.1 -35.0 -32.6 -28.4 -35.4 -39.4 -37.2 -30.2 -20.2 -7.9 1988 -9.0 -20.0 -31.9 -31.3 -30.9 -32.3 -34.3 -28.1 -31.4 -23.2 -18.3 -8.1 1989 -7.8 -20.4 -27.4 -27.8 -34.0 -41.1 -35.9 -38.4 -36.3 -28.4 -14.1 -7.4 1990 -8.6 -20.4 -29.8 -31.3 -33.6 -36.5 -39.0 -41.7 -40.4 -32.0 -18.0 -6.8 1991 -8.9 -14.5 -31.3 -32.0 -34.0 -30.4 -39.0 -38.9 -30.4 -29.0 -17.5 -7.1 1992 -7.4 -20.8 -24.9 -36.2 -30.6 -37.0 -30.3 - - - - - 1993 - -20.5 -31.5 -32.1 -38.6 -32.2 - - - - -14.7 -8.9 1994 -7.6 -19.4 -31.3 -25.4 -39.0 -32.4 -34.2 - - - - - 1995 - - - - - - - - - - - - 1996 - -20.1 -31.9 -28.1 -36.5 -35.6 -37.9 -32.4 -32.9 -31.9 -17.2 -9.1 1997 -10.3 -22.7 -33.1 -36.7 -32.3 -33.5 -39.8 -41.4 -36.4 -24.9 -13.2 -9.5 1998 -11.7 -15.4 -29.5 -38.8 -34.8 -27.6 -38.6 -37.6 -41.4 -29.1 -19.5 -10.5 1999 -9.3 -21.4 -32.4 -39.5 -38.0 -38.7 -32.3 -41.9 -31.0 -27.7 -15.6 -10.3 2000 -11.7 -20.5 -27.4 -30.7 -33.1 -36.0 -33.9 -36.3 -38.3 -31.8 -14.2 -11.5 2001 -13.6 -17.7 -32.4 -32.0 -35.5 -33.1 -32.8 -47.1 -34.3 -31.5 -19.1 -9.5 2002 -9.6 -18.2 -25.3 -32.0 -31.4 -42.3 -43.3 -39.9 -32.1 -27.9 -18.0 -10.5 2003 - - - - - -34.2 -32.6 - - - - - 2004 - - - - - - - - - - - - 2005 - -20.2 -30.1 -32.7 -31.4 -35.4 -33.5 -37.8 -36.4 -27.1 -18.0 -7.2 2006 -10.2 - - - - - - - - - - - 2007 - - - - - - - -36.2 -32.8 - - - 2008 - - - - - - - - - - - - 2009 - - - - - - - - - - - -