1991-2020 Degrees Fahrenheit 1 37.2 36.5 0.7 41 22 1979 2017 2004 2002 normal 2 35.9 35.3 0.6 46 17 1978 2023 2004 2002 top-third 3 36.3 36.1 0.2 39 24 1978 2023 2004 2002 normal 2007 4 39.5 38.6 0.9 46 14 1977 2023 2004 2002 top-third 1983 5 42.7 42.2 0.5 41 19 1977 2017 2004 2002 top-third 1983 6 47.1 46.6 0.5 43 17 1977 2017 2004 2002 top-third 7 51.1 50.8 0.3 43 17 1977 2017 2004 2002 top-third 1972,2013 8 54.2 54.1 0.1 41 19 1977 2017 2004 2002 top-third 9 56.1 56.2 -0.1 38 22 1977 2017 2004 2002 normal 1972 10 57.5 56.9 0.6 46 14 1977 2017 2004 2002 top-third 11 57.3 56.8 0.5 44 16 1977 2017 2004 2002 top-third 12 56.4 55.7 0.7 47 13 1977 2017 2004 2002 top-third 2006,2018 18 52.8 52.7 0.1 41 17 1978 2017 2004 2003 top-third 24 55.5 55.7 -0.2 40 18 1978 2023 2004 2003 top-third 1991,2002 36 55.4 55.7 -0.3 37 19 1979 2022,2023 2004 2004 normal 1993,2003,2004 48 55.7 55.7 0.0 40 14 1980 2023 2004 2005 top-third 2010 60 55.4 55.6 -0.2 33 19 1981 2023 2004 1992 normal 1992