1991-2020 Degrees Fahrenheit 1 43.6 43.3 0.3 45 30 1960 2012 2005 2006 normal 2 35.8 39.5 -3.7 12 63 1978 2012 1993 2006 bottom-third 3 36.7 37.5 -0.8 40 35 1978 2023 2005 2006 normal 4 38.0 37.6 0.4 51 23 1978 2012 2005 2006 top-third 1975 5 40.5 39.5 1.0 56 17 1978 2012 2005 2006 top-third 1953 6 43.0 42.4 0.6 54 19 1978 2002,2012 2005 2006 top-third 1972,1985 7 46.3 46.2 0.1 51 22 1977 2016 2005 2006 top-third 2019 8 50.2 49.9 0.3 55 18 1977 2016 2005 2006 top-third 1972,1983 9 53.4 53.0 0.4 58 15 1977 2012 2005 2006 top-third 10 55.2 54.9 0.3 57 16 1977 2012 2005 2006 top-third 1998,2019 11 56.0 55.7 0.3 58 15 1977 2012 2005 2006 top-third 1991 12 56.0 55.5 0.5 61 12 1968 2012,2020 2005 2006 top-third 1992,1995,2021 18 51.9 51.1 0.8 58 11 1978 2017,2023 2006 2000 top-third 2008 24 56.2 55.5 0.7 60 9 1978 2017 2006 2000 top-third 36 55.8 55.4 0.4 54 11 1979 2022 2006 2000 top-third 48 55.4 55.4 0.0 48 13 1970,1980 2023 2006 2003 top-third 2001,2003,2010,2011 60 55.2 55.3 -0.1 40 18 1970 2020,2023 2005 2006 top-third