Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 1851 "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" 1852 "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" 1853 "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" 1854 "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" 1855 "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" "NA" 1856 19.136 18.625 18.675 19.016 19.936 21.177 22.419 23.123 23.081 22.141 21.056 20.050 1857 19.135 18.417 18.380 18.885 19.712 21.063 22.324 22.916 22.829 21.886 20.756 19.541 1858 18.703 18.165 18.386 19.092 19.836 20.926 22.034 22.850 22.883 22.171 21.202 19.948 1859 18.793 18.360 18.519 19.031 19.836 20.866 22.017 22.987 22.895 22.152 20.989 19.910 1860 19.044 18.371 18.522 18.815 19.921 21.273 22.429 22.966 22.813 22.137 20.925 19.972 1861 18.932 18.376 18.458 19.135 19.949 21.264 22.616 23.231 23.079 22.243 21.150 19.948 1862 18.906 18.325 18.394 18.763 19.575 20.930 21.911 22.663 22.565 21.766 20.585 19.477 1863 18.789 18.447 18.497 18.942 19.781 20.935 21.913 22.633 22.667 21.801 20.761 19.722 1864 18.733 18.137 18.290 18.859 19.834 21.096 22.470 23.283 23.022 22.162 21.129 20.029 1865 19.128 18.744 18.635 18.954 19.790 21.178 22.329 22.976 23.111 22.287 21.157 20.055 1866 18.988 18.671 18.684 19.026 19.936 21.330 22.490 23.195 22.975 22.177 21.208 20.116 1867 19.251 18.779 18.860 19.192 19.921 21.070 22.319 23.009 22.831 22.012 21.057 19.790 1868 19.005 18.629 18.679 19.161 19.953 21.311 22.620 23.145 22.979 21.929 20.891 19.969 1869 18.832 18.593 18.557 19.147 20.052 21.203 22.498 23.079 22.929 22.039 20.905 19.762 1870 18.790 18.513 18.440 18.736 19.742 20.979 22.180 23.046 22.988 22.205 21.126 19.960 1871 18.815 18.387 18.614 19.086 19.917 21.125 22.394 23.007 22.752 21.902 20.950 19.940 1872 18.884 18.455 18.402 18.836 19.953 21.213 22.509 23.335 23.259 22.100 20.923 19.805 1873 19.010 18.516 18.531 18.957 19.730 20.958 22.311 22.998 22.991 22.136 21.021 19.998 1874 19.010 18.401 18.373 18.825 19.797 21.163 22.329 22.943 23.028 22.017 20.904 19.571 1875 18.795 18.583 18.531 18.935 19.948 21.173 22.236 23.050 22.989 22.131 20.906 19.787 1876 18.759 18.443 18.407 18.850 19.716 21.001 22.350 23.136 23.001 22.009 20.887 19.850 1877 18.973 18.680 18.742 19.070 20.046 21.334 22.540 23.330 23.120 22.300 21.273 20.190 1878 19.213 18.861 18.850 19.572 20.319 21.641 22.663 23.557 23.409 22.389 21.348 20.345 1879 19.297 18.908 18.528 18.968 20.043 21.192 22.329 22.988 22.841 22.135 21.046 19.995 1880 19.053 18.536 18.600 18.896 19.661 21.008 22.366 23.077 23.121 22.306 21.129 19.795 1881 19.149 18.659 18.704 19.158 19.918 21.142 22.259 23.023 22.847 22.010 20.679 19.789 1882 18.853 18.441 18.484 18.812 19.677 21.025 22.315 23.051 22.915 22.069 21.002 19.904 1883 18.940 18.379 18.368 18.972 19.845 21.000 22.215 23.005 22.786 21.974 20.986 20.026 1884 19.024 18.405 18.416 18.886 19.768 21.171 22.234 22.983 22.731 21.948 20.657 19.783 1885 18.931 18.598 18.497 18.704 19.656 20.909 22.245 23.110 22.923 22.130 21.015 19.936 1886 19.133 18.684 18.720 19.167 20.060 21.248 22.520 23.065 22.894 22.084 20.993 19.886 1887 18.907 18.475 18.517 18.898 19.874 21.269 22.616 23.210 23.054 22.347 21.197 20.097 1888 19.250 18.741 18.805 19.096 19.969 21.311 22.475 23.161 23.055 22.370 21.149 19.998 1889 19.256 18.818 18.872 19.275 20.143 21.274 22.353 23.099 22.999 22.208 21.186 19.959 1890 19.039 18.578 18.503 18.811 19.685 20.948 22.025 22.706 22.639 22.025 20.741 19.664 1891 18.736 18.482 18.621 19.079 20.014 21.218 22.526 23.111 22.910 22.137 20.778 19.934 1892 19.077 18.693 18.645 18.976 19.710 20.911 22.034 22.907 22.691 21.932 20.742 19.741 1893 18.916 18.519 18.509 18.820 19.706 21.185 22.467 23.178 22.958 22.058 21.045 19.764 1894 18.873 18.410 18.369 18.695 19.487 20.740 22.067 22.782 22.685 21.784 20.713 19.696 1895 18.908 18.495 18.295 18.690 19.641 20.959 22.223 22.927 22.987 22.195 20.920 19.877 1896 18.960 18.614 18.520 19.030 20.107 21.258 22.399 23.105 23.229 22.283 21.075 19.984 1897 19.107 18.715 18.865 19.231 20.013 21.168 22.395 23.043 22.963 22.201 21.017 19.917 1898 19.014 18.642 18.670 19.046 19.942 21.281 22.518 23.166 23.024 22.100 20.904 19.932 1899 18.966 18.535 18.557 19.074 20.057 21.262 22.414 23.300 23.050 22.223 21.236 20.234 1900 19.243 18.794 18.631 19.157 19.856 21.078 22.400 23.033 22.974 22.251 21.085 20.075 1901 19.088 18.781 18.732 19.147 19.944 21.300 22.495 23.219 22.931 22.030 20.964 19.876 1902 18.925 18.564 18.551 18.848 19.774 20.832 22.021 22.868 22.930 22.156 20.928 19.858 1903 19.002 18.652 18.519 18.931 19.722 20.909 22.151 22.596 22.476 21.776 20.808 19.653 1904 18.693 18.227 18.199 18.579 19.471 20.657 21.979 22.694 22.456 21.773 20.850 19.793 1905 18.822 18.420 18.221 18.830 19.807 20.917 22.264 22.902 22.580 21.894 20.782 19.704 1906 18.977 18.572 18.530 18.961 19.712 21.099 22.313 22.982 22.818 22.006 21.034 19.726 1907 18.865 18.257 18.330 18.846 19.725 20.839 22.041 22.733 22.762 21.930 20.827 19.762 1908 18.821 18.375 18.346 18.801 19.713 21.031 22.348 23.059 22.853 22.031 20.902 19.833 1909 18.950 18.468 18.487 18.863 19.871 20.969 22.159 22.970 22.830 22.003 20.767 19.724 1910 18.750 18.362 18.331 18.703 19.539 20.739 22.040 22.796 22.841 21.966 20.984 19.718 1911 18.808 18.362 18.285 18.697 19.540 20.863 22.163 22.992 22.831 22.045 20.833 19.790 1912 18.826 18.358 18.378 18.850 19.771 20.954 22.076 22.666 22.707 21.911 20.843 19.729 1913 18.758 18.408 18.373 18.580 19.439 20.541 21.897 22.628 22.526 21.782 20.612 19.640 1914 18.844 18.303 18.195 18.639 19.627 20.732 21.907 22.695 22.768 22.052 20.886 19.742 1915 18.940 18.508 18.600 19.077 20.155 21.405 22.658 23.280 23.155 22.198 21.067 19.983 1916 19.033 18.528 18.513 18.910 19.915 21.142 22.269 23.054 22.958 22.096 20.836 19.767 1917 18.781 18.280 18.207 18.726 19.645 20.965 22.137 22.881 22.683 21.832 20.759 19.719 1918 18.977 18.458 18.494 18.856 19.663 20.701 21.982 22.685 22.603 21.919 20.782 19.756 1919 18.854 18.577 18.422 18.982 19.740 20.900 22.069 22.888 22.778 22.037 20.858 19.693 1920 18.622 18.235 18.166 18.705 19.655 20.845 22.079 22.779 22.697 21.916 20.660 19.684 1921 18.796 18.368 18.302 18.779 19.659 20.881 22.250 22.838 22.751 22.131 20.828 19.869 1922 18.884 18.403 18.283 18.636 19.595 20.800 21.984 22.779 22.611 21.902 20.743 19.668 1923 18.729 18.187 18.222 18.619 19.635 20.820 22.042 22.665 22.612 21.927 20.881 19.934 1924 18.964 18.451 18.524 18.994 19.963 21.040 22.240 22.955 22.780 21.958 20.783 19.710 1925 18.772 18.342 18.393 18.874 19.843 20.949 22.224 22.964 22.867 22.109 20.929 20.046 1926 19.134 18.762 18.680 19.165 20.049 21.210 22.512 23.150 23.031 22.375 21.130 20.091 1927 19.182 18.734 18.676 19.127 20.117 21.298 22.529 23.257 23.096 22.374 21.243 19.981 1928 19.059 18.565 18.545 18.962 19.945 21.213 22.461 23.205 23.082 22.245 21.057 19.917 1929 19.020 18.562 18.551 19.048 19.821 20.957 22.200 22.951 22.933 22.153 20.997 19.825 1930 18.987 18.491 18.550 18.857 19.823 21.072 22.442 23.178 23.287 22.411 21.268 20.156 1931 19.228 18.735 18.795 19.221 20.162 21.424 22.579 23.262 23.267 22.531 21.176 20.188 1932 19.292 18.901 18.897 19.284 20.094 21.403 22.659 23.501 23.342 22.454 21.257 20.114 1933 19.207 18.831 18.743 19.287 20.233 21.405 22.670 23.398 23.251 22.549 21.203 20.024 1934 19.011 18.488 18.444 18.984 19.833 21.198 22.564 23.200 23.154 22.391 21.143 20.021 1935 19.167 18.545 18.509 19.136 20.089 21.275 22.458 23.128 22.977 22.205 21.148 20.128 1936 19.265 18.828 18.854 19.280 20.118 21.362 22.592 23.339 23.190 22.330 21.150 20.077 1937 19.184 18.770 18.762 19.155 20.084 21.622 23.012 23.719 23.526 22.526 21.390 20.385 1938 19.343 18.839 18.865 19.326 20.159 21.342 22.608 23.428 23.330 22.586 21.455 20.254 1939 19.270 18.768 18.637 19.186 20.063 21.354 22.732 23.456 23.324 22.244 20.987 19.959 1940 19.200 18.500 18.527 19.062 19.963 21.194 22.506 23.241 23.052 22.188 21.010 19.903 1941 19.079 18.791 18.806 19.162 20.001 21.164 22.501 23.418 23.335 22.656 21.537 20.370 1942 19.279 18.897 18.870 19.305 20.176 21.446 22.515 23.288 23.257 22.446 21.345 20.139 1943 19.276 18.799 18.578 18.968 19.846 21.113 22.435 23.161 23.113 22.326 21.295 20.278 1944 19.451 19.023 19.107 19.421 20.265 21.539 22.783 23.593 23.458 22.616 21.426 20.327 1945 19.413 19.057 19.052 19.521 20.286 21.370 22.508 23.259 23.127 22.355 21.342 20.194 1946 19.434 18.903 18.822 19.175 20.069 21.098 22.223 22.990 23.029 22.241 21.096 20.026 1947 18.986 18.588 18.603 19.019 19.828 21.050 22.275 23.059 22.999 22.170 21.211 20.097 1948 19.148 18.691 18.725 19.049 19.982 21.260 22.395 23.139 22.999 22.270 21.301 20.128 1949 19.319 18.881 18.738 19.221 19.965 21.209 22.509 23.266 23.125 22.368 21.277 20.186 1950 19.279 18.690 18.597 18.995 19.934 21.168 22.385 23.187 23.067 22.177 21.253 20.160 1951 19.274 18.725 18.718 19.297 20.167 21.502 22.864 23.473 23.310 22.530 21.350 20.249 1952 19.346 18.912 18.938 19.321 20.178 21.599 22.817 23.576 23.426 22.628 21.429 20.418 1953 19.442 18.917 18.852 19.447 20.342 21.494 22.791 23.433 23.346 22.424 21.425 20.337 1954 19.407 18.830 18.814 19.123 20.073 21.321 22.406 23.163 23.058 22.246 21.157 20.031 1955 19.259 18.777 18.757 19.234 20.182 21.418 22.722 23.355 23.275 22.560 21.572 20.341 1956 19.372 18.835 18.733 19.205 19.951 20.963 22.366 23.084 22.985 22.241 21.102 20.107 1957 19.107 18.636 18.702 19.070 19.890 21.217 22.499 23.388 23.298 22.437 21.276 20.170 1958 19.239 18.934 19.068 19.493 20.215 21.454 22.625 23.350 23.292 22.441 21.379 20.312 1959 19.293 18.862 18.699 19.146 20.023 21.176 22.433 23.203 23.208 22.404 21.248 20.206 1960 19.372 18.967 18.818 19.249 20.321 21.556 22.737 23.529 23.296 22.591 21.450 20.236 1961 19.259 18.835 18.880 19.382 20.215 21.273 22.451 23.232 23.090 22.326 21.269 20.314 1962 19.350 18.908 18.900 19.245 20.047 21.172 22.464 23.136 23.094 22.366 21.251 20.294 1963 19.361 18.924 18.871 19.264 19.942 21.198 22.439 23.128 22.890 22.231 21.150 20.046 1964 19.131 18.782 18.780 19.016 20.070 21.252 22.333 22.970 22.876 22.034 21.044 19.987 1965 19.010 18.587 18.665 19.068 19.934 21.124 22.292 22.996 22.876 22.060 20.936 19.988 1966 19.136 18.777 18.735 19.211 20.036 21.209 22.427 23.166 23.100 22.324 21.218 20.194 1967 19.296 18.857 18.714 19.155 19.850 20.995 22.255 23.048 23.007 22.213 20.983 19.964 1968 18.970 18.573 18.542 19.017 19.916 20.997 22.259 23.001 22.956 22.202 21.113 19.992 1969 19.156 18.879 18.960 19.325 20.053 21.290 22.584 23.117 23.001 22.133 21.100 20.091 1970 19.212 18.729 18.775 19.198 19.998 21.082 22.293 23.080 22.974 22.125 20.986 19.915 1971 18.979 18.487 18.448 18.768 19.722 20.905 22.146 22.787 22.748 22.089 20.986 19.820 1972 18.910 18.402 18.323 18.858 19.582 20.782 22.124 22.843 22.815 22.041 20.955 19.780 1973 18.857 18.393 18.421 18.923 19.885 21.098 22.399 23.096 22.989 22.115 21.026 19.896 1974 18.959 18.505 18.366 18.667 19.557 20.829 21.990 22.764 22.618 21.825 20.812 19.776 1975 18.964 18.453 18.461 18.848 19.671 20.984 22.236 23.050 22.790 21.982 20.900 19.818 1976 18.855 18.353 18.280 18.770 19.575 20.798 22.205 23.052 22.936 22.046 20.828 19.711 1977 18.854 18.465 18.594 18.982 19.896 21.178 22.409 23.096 22.900 22.118 21.104 19.941 1978 19.140 18.654 18.621 19.007 19.865 20.955 22.241 23.017 22.945 22.138 21.131 19.967 1979 19.057 18.653 18.555 18.969 19.955 21.249 22.426 23.132 23.029 22.261 21.168 20.093 1980 19.251 18.729 18.648 19.209 20.205 21.403 22.574 23.274 23.134 22.291 21.059 19.906 1981 19.078 18.635 18.795 19.122 19.999 21.240 22.437 23.143 23.113 22.173 21.129 20.152 1982 19.179 18.737 18.714 19.039 19.888 21.120 22.306 22.955 22.849 22.001 20.851 19.783 1983 18.966 18.713 18.877 19.283 20.043 21.253 22.525 23.106 22.938 22.168 21.110 20.165 1984 19.163 18.737 18.677 19.070 19.921 20.983 22.268 23.035 22.949 22.035 20.853 19.855 1985 18.917 18.497 18.447 18.828 19.755 21.188 22.391 22.993 22.916 22.124 20.980 19.841 1986 18.934 18.555 18.518 18.913 19.866 21.062 22.301 23.004 22.949 22.055 20.880 19.802 1987 18.996 18.613 18.773 19.259 20.152 21.513 22.826 23.555 23.363 22.426 21.209 20.221 1988 19.237 18.720 18.802 19.289 20.238 21.489 22.670 23.274 23.079 22.209 21.125 20.007 1989 19.052 18.676 18.564 18.959 19.957 21.410 22.728 23.392 23.081 22.256 21.134 20.028 1990 18.984 18.678 18.642 19.132 20.046 21.269 22.534 23.332 23.320 22.500 21.240 20.154 1991 19.094 18.725 18.753 19.115 19.948 21.190 22.445 23.177 23.135 22.126 21.029 19.968 1992 19.093 18.743 18.724 19.057 19.878 21.177 22.338 22.906 22.809 22.091 20.958 19.900 1993 19.043 18.654 18.573 19.071 19.941 21.152 22.279 23.058 23.018 22.151 20.979 19.899 1994 19.001 18.539 18.547 19.054 19.910 21.113 22.336 23.064 23.045 22.349 21.281 20.100 1995 19.230 18.814 18.851 19.330 20.383 21.705 22.882 23.479 23.243 22.496 21.419 20.233 1996 19.284 18.818 18.770 19.261 20.052 21.212 22.460 23.290 23.189 22.250 21.126 20.048 1997 19.213 18.821 18.839 19.262 20.157 21.354 22.637 23.316 23.297 22.547 21.349 20.332 1998 19.433 19.149 19.157 19.554 20.502 21.834 23.067 23.822 23.613 22.792 21.631 20.486 1999 19.358 18.919 18.911 19.320 20.297 21.541 22.785 23.622 23.393 22.438 21.274 20.229 2000 19.227 18.825 18.944 19.313 20.240 21.337 22.657 23.414 23.306 22.375 21.269 20.092 2001 19.192 18.846 18.870 19.265 20.124 21.554 22.727 23.498 23.503 22.679 21.479 20.428 2002 19.494 19.038 18.998 19.304 20.092 21.245 22.530 23.430 23.296 22.536 21.344 20.225 2003 19.371 18.858 18.960 19.351 20.296 21.572 22.881 23.746 23.667 22.849 21.551 20.449 2004 19.532 19.086 19.011 19.389 20.143 21.541 22.828 23.641 23.454 22.669 21.558 20.417 2005 19.439 19.004 19.142 19.576 20.438 21.695 23.053 23.769 23.639 22.666 21.466 20.443 2006 19.449 18.952 18.918 19.484 20.458 21.707 22.983 23.741 23.590 22.767 21.614 20.399 2007 19.499 19.099 18.991 19.448 20.264 21.465 22.740 23.392 23.325 22.595 21.515 20.343 2008 19.361 19.014 19.028 19.337 20.326 21.639 22.818 23.508 23.426 22.538 21.344 20.261 2009 19.280 18.730 18.707 19.165 20.096 21.506 22.842 23.492 23.288 22.610 21.414 20.327 2010 19.383 19.071 19.162 19.728 20.624 21.833 23.068 23.872 23.686 22.771 21.588 20.458