1991-2020 Degrees Fahrenheit 1 66.4 63.5 2.9 54 6 1993 2005 2014 2015 top-tenth 2 70.0 67.3 2.7 58 2 1992 2005 2015 2005 top-tenth 1998 3 71.4 69.1 2.3 59 1 1992 2005,2016 2015 2005 highest 2005 4 71.1 69.1 2.0 58 2 1992 2005 2015 2005 top-tenth 5 69.0 67.1 1.9 55 5 1992 2018 2015 2012 top-tenth 6 65.2 63.8 1.4 53 7 1992 2010 2015 2012 top-third 2007 7 61.7 59.8 1.9 56 4 1992 2012 2015 2012 top-tenth 8 57.7 55.7 2.0 56 4 1978 2012 2015 2012 top-tenth 9 54.2 52.2 2.0 56 4 1978 2012 2015 2012 top-tenth 10 52.7 50.1 2.6 57 3 1978 2012 2015 2012 top-tenth 11 52.0 49.1 2.9 57 2 1978 2012 2015 2012 top-tenth 12 52.0 49.3 2.7 57 2 1978 2012 2015 2012 top-tenth 18 55.9 54.2 1.7 57 2 1979 2012 2015 2012 top-tenth 24 49.7 49.3 0.4 44 14 1979 2017 2015 2013 top-third 2005 36 48.6 49.3 -0.7 26 31 1979 2012 2015 2014 normal 1976 48 48.8 49.3 -0.5 31 25 1980 2013 1998 2015 normal 1976,1998 60 49.7 49.2 0.5 47 8 1982 2002 2015 2014 top-third 2010,2019