Year,Value,Contiguous U.S. (Lower 48),Precip,Jan-Jul,(in.)
1940,19.135
1941,18.108
1942,17.645
1943,17.328
1944,19.386
1945,21.316
1946,19.186
1947,19.202
1948,19.985
1949,20.917
1950,20.72
1951,19.548
1952,17.62
1953,19.777
1954,16.833
1955,17.385
1956,16.855
1957,21.126
1958,20.529
1959,18.618
1960,18.45
1961,19.079
1962,17.798
1963,16.298
1964,18.168
1965,17.837
1966,15.504
1967,17.813
1968,17.208
1969,18.6
1970,16.581
1971,16.555
1972,17.592
1973,21.599
1974,18.335
1975,20.907
1976,17.725
1977,16.879
1978,19.672
1979,21.45
1980,19.638
1981,19.09
1982,21.958
1983,22.373
1984,19.958
1985,17.965
1986,19.379
1987,19.262
1988,16.025
1989,20.141
1990,21.183
1991,20.968
1992,19.588
1993,22.757
1994,19.435
1995,21.909
1996,19.992
1997,20.966
1998,22.328
1999,19.791
2000,18.38
2001,17.939
2002,16.792
2003,18.991
2004,19.087
2005,18.863
2006,16.607
2007,17.514
2008,18.956
2009,18.784
2010,19.712
2011,19.045
2012,16.392
2013,19.122
2014,18.149
2015,19.155
2016,18.766
2017,21.738
2018,19.817
2019,23.151
2020,19.771
2021,19.26
2022,17.769
2023,19.274
2024,21.29
2025,19.707