YEAR Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual 24-hr Avg. 1990 8561 9083 9479 9673 10423 10359 9901 9655 9474 9552 9111 8428 9476 1991 8241 9050 9245 9880 10265 10162 10023 9722 11210 10919 9579 9577 9825 1992 9340 9812 9976 10587 10856 11061 10410 10863 11463 10829 9718 10071 10444 1993 9136 9880 10506 10948 11078 11520 11030 10757 11051 10728 9999 9983 10553 1994 9605 9965 10755 11660 11161 11245 9909 10304 10652 10501 9822 9816 10449 1995 9482 9998 10329 10799 11278 11322 10814 10964 10727 10731 10101 10215 10563 1996 9380 10150 10605 11142 11758 12225 11511 11272 11639 11111 10957 10017 10981 1997 10039 10564 10643 11603 12109 11961 11325 11317 11521 11397 10494 10258 11103 1998 10072 10527 10679 11391 11757 11825 11546 11347 11226 11075 10443 10474 11030 1999 9858 10243 10867 11206 11821 12004 11385 11189 11364 11261 10393 10228 10985 2000 9823 10259 10479 11061 11368 11347 11085 10973 10862 10505 9997 9619 10615 2001 9202 9833 10255 10527 10853 10960 11275 11135 11145 10799 10192 9833 10501 2002 9656 9904 10255 10925 11996 11186 10861 10225 10386 10194 9712 9617 10410 2003 9448 9550 9414 10441 11474 10512 10184 11097 12173 9956 8912 9597 10230 2004 9034 9057 9764 10277 10373 10676 10058 10008 10079 9656 9231 9382 9800 2005 8647 9316 9546 10195 10319 10475 9972 10261 10099 10016 9389 9275 9793 2006 8761 9320 9519 9975 10528 9936 9578 10265 10288 9235 9094 2007 8805 9275 9498 10194 10499 10133 9605 9639 10349 9593 8390 8991 9581 2008 9235 8957 9987 10255 8235 8086 8145 8334 9041 8426 8674 2009 8260 8724 8641 9760 10239 9381 9211 9192 9608 8794 8786 2010 8464 9060 9116 9997 10665 2011 9682 9953 9769