1991-2020 Degrees Fahrenheit 1 25.4 29.9 -4.5 20 55 1955 1999 1986 1990 bottom-third 2 32.8 36.7 -3.9 6 69 1985 1963 1985 1990 bottom-tenth 3 40.8 43.8 -3.0 11 64 1985 1963 1986 1990 bottom-third 4 48.6 49.8 -1.2 28 47 1985 1963,2021 1986 1990 normal 5 52.8 53.7 -0.9 28 47 1985 2021 1986 1990 normal 1970,1979,1984,2009 6 54.7 55.1 -0.4 38 36 1985 2021 1986 1990 normal 1954,2004,2010 7 54.7 54.7 0.0 43 31 1951 2021 1986 1990 normal 1952,1956 8 53.2 53.0 0.2 44 30 1950 1988,2021 1986 1990 normal 2011 9 51.0 50.5 0.5 53 21 1951 2021 1989 1990 top-third 2005 10 48.9 47.3 1.6 63 11 1951 2012 1990 1990 top-third 1990 11 45.4 44.5 0.9 56 18 1950 2012 1989 1990 top-third 2001 12 42.6 42.4 0.2 51 22 1950 2021 1989 1990 top-third 2008 18 47.2 46.6 0.6 52 20 1951 2021 1989 1990 top-third 1989,2005,2020 24 43.1 42.3 0.8 55 16 1951 1988 1990 1989 top-third 36 42.7 42.3 0.4 54 15 1952 1989,2017 1987 1990 top-third 2005 48 43.4 42.3 1.1 60 7 1952 1990 1988 1990 top-tenth 2000 60 43.9 42.4 1.5 64 1 1953 1991 1990 1991 highest