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 19.159 18.647 18.697 19.040 19.958 21.199 22.439 23.143 23.101 22.163 21.079 20.072 1857 19.157 18.439 18.402 18.907 19.733 21.084 22.343 22.935 22.849 21.907 20.779 19.563 1858 18.725 18.187 18.409 19.114 19.858 20.947 22.054 22.869 22.903 22.192 21.224 19.971 1859 18.815 18.383 18.542 19.055 19.859 20.888 22.036 23.006 22.915 22.174 21.011 19.933 1860 19.066 18.394 18.545 18.838 19.943 21.294 22.448 22.984 22.832 22.158 20.947 19.995 1861 18.953 18.399 18.481 19.157 19.971 21.285 22.635 23.249 23.099 22.265 21.173 19.971 1862 18.928 18.348 18.417 18.787 19.597 20.953 21.930 22.682 22.586 21.788 20.607 19.500 1863 18.811 18.469 18.519 18.964 19.805 20.956 21.932 22.652 22.687 21.821 20.783 19.745 1864 18.755 18.160 18.312 18.882 19.856 21.116 22.490 23.302 23.042 22.184 21.151 20.052 1865 19.151 18.766 18.658 18.977 19.812 21.200 22.349 22.996 23.132 22.309 21.180 20.079 1866 19.012 18.694 18.707 19.048 19.958 21.352 22.510 23.214 22.995 22.199 21.232 20.139 1867 19.275 18.802 18.883 19.215 19.944 21.092 22.338 23.028 22.852 22.033 21.079 19.813 1868 19.027 18.652 18.702 19.183 19.976 21.333 22.639 23.164 22.999 21.950 20.913 19.991 1869 18.855 18.615 18.579 19.170 20.074 21.225 22.517 23.098 22.950 22.060 20.927 19.784 1870 18.813 18.535 18.462 18.759 19.765 21.000 22.199 23.065 23.008 22.226 21.148 19.983 1871 18.838 18.411 18.637 19.109 19.939 21.146 22.414 23.025 22.772 21.924 20.973 19.962 1872 18.906 18.477 18.424 18.859 19.975 21.234 22.529 23.355 23.278 22.121 20.946 19.827 1873 19.032 18.538 18.554 18.980 19.752 20.980 22.331 23.017 23.010 22.157 21.043 20.021 1874 19.032 18.423 18.396 18.847 19.819 21.184 22.350 22.962 23.048 22.038 20.927 19.593 1875 18.818 18.605 18.553 18.958 19.970 21.194 22.256 23.069 23.009 22.153 20.928 19.810 1876 18.781 18.466 18.430 18.873 19.738 21.022 22.371 23.156 23.022 22.030 20.909 19.873 1877 18.997 18.703 18.765 19.093 20.069 21.356 22.560 23.349 23.141 22.322 21.296 20.214 1878 19.235 18.884 18.873 19.595 20.342 21.663 22.683 23.576 23.429 22.410 21.371 20.368 1879 19.320 18.931 18.550 18.991 20.066 21.214 22.350 23.007 22.861 22.156 21.069 20.018 1880 19.076 18.559 18.623 18.919 19.683 21.028 22.385 23.095 23.140 22.328 21.150 19.818 1881 19.172 18.682 18.727 19.181 19.941 21.164 22.280 23.043 22.867 22.032 20.702 19.811 1882 18.875 18.463 18.507 18.836 19.699 21.047 22.336 23.070 22.935 22.089 21.025 19.926 1883 18.962 18.401 18.391 18.995 19.867 21.022 22.235 23.024 22.807 21.996 21.008 20.048 1884 19.047 18.427 18.439 18.909 19.790 21.193 22.254 23.002 22.752 21.970 20.680 19.806 1885 18.954 18.620 18.520 18.727 19.678 20.930 22.265 23.130 22.943 22.153 21.037 19.959 1886 19.156 18.707 18.743 19.189 20.083 21.270 22.540 23.084 22.915 22.105 21.016 19.909 1887 18.930 18.498 18.540 18.921 19.898 21.290 22.636 23.229 23.073 22.369 21.220 20.120 1888 19.272 18.764 18.827 19.118 19.992 21.332 22.495 23.180 23.075 22.392 21.171 20.021 1889 19.279 18.841 18.895 19.298 20.166 21.295 22.373 23.118 23.019 22.229 21.209 19.982 1890 19.062 18.601 18.525 18.833 19.708 20.970 22.044 22.725 22.658 22.046 20.764 19.686 1891 18.758 18.504 18.643 19.102 20.036 21.239 22.546 23.130 22.930 22.158 20.801 19.957 1892 19.100 18.716 18.667 18.999 19.732 20.932 22.055 22.926 22.711 21.953 20.765 19.763 1893 18.938 18.541 18.531 18.842 19.729 21.206 22.487 23.198 22.978 22.079 21.068 19.787 1894 18.896 18.432 18.391 18.718 19.509 20.761 22.086 22.801 22.705 21.806 20.735 19.719 1895 18.931 18.519 18.318 18.712 19.663 20.981 22.242 22.946 23.008 22.217 20.942 19.900 1896 18.983 18.637 18.543 19.054 20.129 21.280 22.419 23.124 23.249 22.305 21.098 20.006 1897 19.130 18.738 18.888 19.254 20.036 21.189 22.415 23.062 22.984 22.223 21.039 19.940 1898 19.036 18.664 18.693 19.070 19.965 21.302 22.536 23.185 23.044 22.122 20.926 19.955 1899 18.989 18.558 18.580 19.097 20.080 21.283 22.434 23.319 23.071 22.245 21.259 20.257 1900 19.266 18.817 18.654 19.180 19.879 21.100 22.420 23.052 22.994 22.273 21.107 20.098 1901 19.110 18.803 18.755 19.170 19.966 21.321 22.514 23.238 22.951 22.052 20.986 19.899 1902 18.948 18.587 18.574 18.872 19.797 20.853 22.041 22.887 22.950 22.178 20.951 19.881 1903 19.025 18.674 18.542 18.954 19.745 20.931 22.171 22.616 22.496 21.797 20.830 19.676 1904 18.716 18.249 18.222 18.602 19.493 20.679 21.998 22.714 22.476 21.795 20.872 19.816 1905 18.845 18.442 18.244 18.854 19.830 20.938 22.283 22.921 22.600 21.915 20.804 19.727 1906 19.000 18.595 18.553 18.984 19.735 21.120 22.333 23.001 22.838 22.028 21.057 19.749 1907 18.888 18.280 18.353 18.869 19.748 20.860 22.061 22.752 22.782 21.952 20.849 19.785 1908 18.844 18.398 18.369 18.823 19.735 21.052 22.368 23.077 22.873 22.052 20.924 19.857 1909 18.973 18.490 18.510 18.886 19.894 20.989 22.179 22.989 22.850 22.024 20.790 19.747 1910 18.774 18.384 18.354 18.727 19.562 20.760 22.060 22.815 22.861 21.987 21.006 19.741 1911 18.830 18.385 18.308 18.719 19.562 20.884 22.183 23.012 22.851 22.066 20.856 19.813 1912 18.849 18.380 18.401 18.873 19.793 20.975 22.097 22.685 22.727 21.932 20.866 19.752 1913 18.781 18.431 18.396 18.603 19.462 20.562 21.917 22.647 22.546 21.803 20.635 19.663 1914 18.867 18.326 18.218 18.662 19.650 20.754 21.927 22.714 22.787 22.074 20.909 19.764 1915 18.963 18.531 18.622 19.101 20.177 21.427 22.678 23.299 23.176 22.218 21.090 20.006 1916 19.055 18.551 18.536 18.933 19.937 21.164 22.288 23.073 22.977 22.118 20.858 19.789 1917 18.804 18.303 18.230 18.748 19.667 20.987 22.157 22.900 22.702 21.854 20.782 19.741 1918 19.000 18.480 18.517 18.878 19.685 20.722 22.003 22.705 22.623 21.941 20.805 19.780 1919 18.878 18.600 18.445 19.005 19.762 20.922 22.089 22.907 22.798 22.059 20.880 19.716 1920 18.645 18.258 18.189 18.728 19.677 20.866 22.100 22.798 22.717 21.937 20.683 19.706 1921 18.819 18.391 18.325 18.803 19.682 20.903 22.270 22.858 22.771 22.153 20.851 19.892 1922 18.907 18.425 18.305 18.659 19.617 20.822 22.004 22.798 22.631 21.923 20.765 19.691 1923 18.752 18.210 18.245 18.642 19.657 20.842 22.062 22.684 22.632 21.948 20.903 19.957 1924 18.987 18.474 18.547 19.018 19.986 21.061 22.260 22.975 22.800 21.979 20.805 19.733 1925 18.794 18.364 18.415 18.898 19.866 20.971 22.244 22.983 22.887 22.130 20.952 20.069 1926 19.157 18.784 18.703 19.188 20.071 21.232 22.531 23.169 23.051 22.397 21.152 20.114 1927 19.205 18.756 18.698 19.149 20.139 21.320 22.548 23.276 23.117 22.396 21.266 20.003 1928 19.082 18.588 18.568 18.985 19.967 21.234 22.481 23.223 23.101 22.267 21.080 19.940 1929 19.043 18.585 18.574 19.071 19.843 20.979 22.219 22.970 22.952 22.175 21.020 19.847 1930 19.010 18.513 18.572 18.880 19.845 21.094 22.461 23.197 23.307 22.433 21.290 20.179 1931 19.251 18.757 18.818 19.244 20.184 21.446 22.599 23.282 23.286 22.553 21.199 20.211 1932 19.315 18.924 18.920 19.308 20.116 21.424 22.678 23.520 23.362 22.475 21.280 20.137 1933 19.230 18.853 18.766 19.310 20.257 21.426 22.690 23.417 23.271 22.570 21.225 20.047 1934 19.033 18.510 18.468 19.008 19.856 21.219 22.583 23.219 23.173 22.413 21.166 20.042 1935 19.190 18.567 18.532 19.158 20.111 21.297 22.478 23.146 22.997 22.226 21.171 20.151 1936 19.287 18.850 18.877 19.303 20.141 21.383 22.613 23.358 23.210 22.351 21.173 20.100 1937 19.207 18.793 18.785 19.179 20.106 21.644 23.031 23.738 23.547 22.547 21.412 20.409 1938 19.366 18.862 18.888 19.350 20.181 21.364 22.629 23.448 23.350 22.607 21.477 20.276 1939 19.292 18.791 18.659 19.209 20.086 21.375 22.751 23.475 23.344 22.265 21.008 19.981 1940 19.223 18.522 18.550 19.085 19.986 21.216 22.525 23.261 23.072 22.210 21.033 19.926 1941 19.102 18.813 18.829 19.185 20.024 21.185 22.520 23.437 23.355 22.677 21.560 20.393 1942 19.301 18.920 18.892 19.328 20.199 21.467 22.535 23.306 23.277 22.467 21.366 20.161 1943 19.299 18.821 18.601 18.990 19.870 21.134 22.454 23.180 23.133 22.348 21.316 20.301 1944 19.473 19.046 19.129 19.444 20.288 21.561 22.803 23.611 23.477 22.638 21.449 20.351 1945 19.436 19.080 19.075 19.545 20.309 21.392 22.529 23.278 23.148 22.376 21.365 20.217 1946 19.457 18.925 18.844 19.198 20.092 21.120 22.243 23.010 23.049 22.262 21.119 20.047 1947 19.008 18.611 18.626 19.043 19.852 21.071 22.295 23.078 23.019 22.190 21.234 20.119 1948 19.170 18.713 18.748 19.073 20.005 21.282 22.415 23.157 23.020 22.291 21.323 20.151 1949 19.341 18.904 18.761 19.244 19.988 21.230 22.528 23.285 23.145 22.391 21.300 20.209 1950 19.302 18.713 18.620 19.018 19.956 21.189 22.404 23.206 23.088 22.199 21.275 20.182 1951 19.297 18.747 18.741 19.319 20.190 21.525 22.884 23.493 23.330 22.551 21.372 20.272 1952 19.369 18.935 18.961 19.345 20.201 21.621 22.837 23.595 23.445 22.649 21.451 20.440 1953 19.465 18.940 18.875 19.470 20.365 21.515 22.812 23.452 23.366 22.445 21.447 20.360 1954 19.429 18.853 18.837 19.146 20.095 21.342 22.425 23.182 23.078 22.268 21.179 20.054 1955 19.281 18.801 18.780 19.257 20.205 21.439 22.742 23.375 23.295 22.582 21.595 20.364 1956 19.394 18.857 18.755 19.228 19.973 20.984 22.386 23.104 23.006 22.263 21.125 20.129 1957 19.129 18.659 18.725 19.093 19.912 21.239 22.519 23.407 23.318 22.457 21.298 20.193 1958 19.262 18.958 19.092 19.516 20.238 21.476 22.646 23.368 23.312 22.462 21.402 20.335 1959 19.316 18.885 18.722 19.169 20.046 21.197 22.452 23.222 23.227 22.425 21.270 20.227 1960 19.395 18.990 18.840 19.272 20.344 21.578 22.757 23.547 23.316 22.612 21.472 20.259 1961 19.281 18.857 18.903 19.404 20.238 21.294 22.470 23.251 23.110 22.348 21.291 20.337 1962 19.373 18.931 18.923 19.268 20.070 21.193 22.484 23.155 23.114 22.387 21.274 20.317 1963 19.384 18.948 18.894 19.287 19.965 21.220 22.459 23.148 22.911 22.253 21.173 20.069 1964 19.154 18.805 18.802 19.040 20.093 21.273 22.353 22.989 22.895 22.055 21.066 20.011 1965 19.033 18.609 18.687 19.091 19.956 21.146 22.312 23.016 22.896 22.081 20.959 20.011 1966 19.158 18.800 18.758 19.235 20.059 21.230 22.447 23.185 23.121 22.345 21.241 20.217 1967 19.318 18.880 18.737 19.179 19.873 21.017 22.275 23.067 23.026 22.235 21.006 19.986 1968 18.993 18.596 18.564 19.041 19.939 21.018 22.278 23.021 22.976 22.224 21.135 20.015 1969 19.179 18.902 18.984 19.348 20.077 21.312 22.604 23.136 23.022 22.155 21.122 20.114 1970 19.235 18.752 18.798 19.222 20.022 21.104 22.313 23.099 22.994 22.147 21.008 19.939 1971 19.002 18.511 18.472 18.792 19.744 20.926 22.167 22.807 22.768 22.110 21.009 19.842 1972 18.933 18.426 18.345 18.882 19.605 20.804 22.145 22.862 22.835 22.063 20.978 19.803 1973 18.880 18.416 18.444 18.946 19.908 21.120 22.419 23.115 23.010 22.136 21.049 19.919 1974 18.981 18.528 18.389 18.690 19.580 20.850 22.010 22.784 22.638 21.847 20.834 19.798 1975 18.988 18.476 18.484 18.871 19.695 21.006 22.257 23.069 22.810 22.004 20.923 19.841 1976 18.878 18.377 18.303 18.793 19.597 20.820 22.223 23.073 22.957 22.067 20.851 19.734 1977 18.876 18.487 18.617 19.005 19.919 21.199 22.428 23.115 22.921 22.140 21.127 19.964 1978 19.163 18.676 18.644 19.031 19.888 20.977 22.261 23.036 22.966 22.160 21.153 19.989 1979 19.080 18.676 18.578 18.992 19.978 21.271 22.447 23.152 23.050 22.283 21.191 20.116 1980 19.274 18.752 18.670 19.232 20.228 21.425 22.594 23.293 23.154 22.312 21.082 19.929 1981 19.102 18.657 18.818 19.144 20.023 21.262 22.457 23.163 23.134 22.195 21.152 20.175 1982 19.203 18.759 18.738 19.062 19.911 21.142 22.326 22.974 22.869 22.024 20.874 19.806 1983 18.989 18.736 18.901 19.307 20.066 21.275 22.546 23.125 22.959 22.190 21.133 20.188 1984 19.187 18.760 18.700 19.093 19.944 21.005 22.288 23.055 22.969 22.057 20.876 19.878 1985 18.941 18.520 18.470 18.851 19.777 21.210 22.411 23.013 22.937 22.146 21.003 19.864 1986 18.956 18.577 18.541 18.937 19.889 21.083 22.321 23.023 22.969 22.077 20.902 19.825 1987 19.019 18.635 18.797 19.282 20.175 21.535 22.846 23.574 23.384 22.448 21.232 20.244 1988 19.260 18.743 18.824 19.312 20.261 21.511 22.691 23.294 23.099 22.230 21.148 20.030 1989 19.075 18.698 18.587 18.981 19.979 21.431 22.748 23.412 23.101 22.277 21.157 20.051 1990 19.007 18.701 18.665 19.155 20.069 21.290 22.555 23.351 23.341 22.522 21.262 20.177 1991 19.118 18.748 18.775 19.138 19.970 21.211 22.465 23.196 23.156 22.148 21.053 19.991 1992 19.116 18.764 18.746 19.081 19.901 21.198 22.358 22.925 22.829 22.113 20.980 19.923 1993 19.066 18.677 18.595 19.094 19.964 21.174 22.300 23.078 23.038 22.174 21.001 19.923 1994 19.024 18.562 18.570 19.077 19.933 21.134 22.356 23.083 23.065 22.370 21.304 20.123 1995 19.253 18.837 18.873 19.352 20.406 21.727 22.903 23.500 23.264 22.517 21.442 20.256 1996 19.307 18.841 18.793 19.284 20.075 21.234 22.480 23.308 23.208 22.271 21.148 20.071 1997 19.236 18.844 18.862 19.285 20.180 21.376 22.657 23.335 23.316 22.569 21.372 20.355 1998 19.457 19.173 19.181 19.578 20.526 21.856 23.087 23.841 23.634 22.814 21.655 20.509 1999 19.381 18.941 18.933 19.343 20.319 21.563 22.805 23.642 23.413 22.459 21.297 20.252 2000 19.249 18.848 18.967 19.336 20.262 21.359 22.677 23.433 23.326 22.396 21.291 20.115 2001 19.215 18.869 18.893 19.288 20.147 21.576 22.747 23.518 23.524 22.700 21.502 20.451 2002 19.517 19.061 19.021 19.327 20.115 21.266 22.550 23.448 23.316 22.557 21.366 20.247 2003 19.394 18.881 18.982 19.374 20.318 21.594 22.901 23.765 23.687 22.871 21.573 20.472 2004 19.555 19.108 19.035 19.413 20.165 21.562 22.847 23.660 23.474 22.690 21.580 20.440 2005 19.462 19.027 19.164 19.600 20.461 21.716 23.072 23.788 23.660 22.687 21.489 20.467 2006 19.472 18.975 18.940 19.506 20.480 21.729 23.003 23.761 23.611 22.788 21.637 20.422