1991-2020 Degrees Fahrenheit 1 22.5 23.5 -1.0 42 43 1949 2006 1997 2000 normal 2 20.4 23.4 -3.0 25 59 1949 1958 1997 2000 bottom-third 3 21.6 26.8 -5.2 12 72 1979 2021 1997 2000 bottom-third 2023 4 27.5 31.7 -4.2 10 73 1979 2000 1997 2000 bottom-third 5 33.6 37.2 -3.6 13 70 1979 2022 1997 2000 bottom-third 1942,1969 6 39.8 42.6 -2.8 17 66 1986 2021 1997 2000 bottom-third 1978 7 44.5 46.7 -2.2 25 58 1979 2022 1997 2000 bottom-third 8 46.6 48.7 -2.1 26 57 1952,1979 2022 1997 2000 bottom-third 2010 9 47.6 49.3 -1.7 25 58 1979 2022 1997 2000 bottom-third 1942,1994,2010,2011 10 47.7 48.9 -1.2 32 51 1952 2022 1997 2000 normal 11 46.9 47.8 -0.9 37 44 1952 2016 1997 2000 normal 1947,2020 12 45.7 46.1 -0.4 48 33 1952 2016 1997 2000 normal 1953,1993,2023 18 45.6 44.9 0.7 68 11 1952 2013,2022 1998 2000 top-third 1954 24 46.5 46.0 0.5 63 14 1950 2017 1998 2000 top-third 2006 36 46.8 46.0 0.8 67 6 1952 2018 2000 2000 top-tenth 2000,2007 48 46.6 46.0 0.6 64 5 1952 2019 2000 2001 top-tenth 2007 60 45.8 46.0 -0.2 46 19 1952,1953 2008,2009,2020 2000 1993 top-third 1991