YEAR Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual 24-hr Avg. 1990 11450 12294 13144 13256 15335 16119 13587 13710 12568 13066 12470 11350 13199 1991 11627 12548 13073 13682 13712 13703 12748 12875 12501 15091 14403 13126 13260 1992 12898 13819 17200 17618 17651 17887 16668 15323 14857 14981 14193 13935 15632 1993 11437 13049 16247 16655 16655 16126 16212 15132 15444 15700 15812 15698 15359 1994 13883 14727 16139 16315 16554 17127 16486 16558 16425 16287 15585 15040 15932 1995 15287 16182 16760 17274 17262 17538 16602 17262 18569 17539 16928 16068 16939 1996 15607 15015 16405 16543 1997 16614 17524 18597 19241 19888 20448 19110 18940 18474 18056 18093 17849 18570 1998 17024 18664 19147 19528 19307 20006 19683 19642 19665 19637 19590 16721 19051 1999 18962 19097 20387 20970 21147 21368 20783 21310 21102 21514 20314 19547 20542 2000 19031 20402 20943 21924 21913 21743 21624 23652 22026 21788 20739 20231 21335 2001 23310 20675 22806 22526 22452 22070 22315 21983 21071 21119 20253 19405 21665 2002 23832 26466 27135 28502 28559 27851 27463 28208 27656 28218 26951 25953 27233 2003 24187 20938 20810 21714 22008 22668 21282 21534 21183 21381 20230 20299 21520 2004 19145 20665 21951 22910 23658 22097 21846 22862 22928 21420 21533 21679 21891 2005 20826 25751 23850 22875 23023 23258 25180 27395 22673 22795 22499 22208 23528 2006 21919 23989 28555 31657 32256 31786 30102 28091 26869 26608 25773 21856 27455 2007 19206 20710 21128 21129 20638 19992 21180 20465 20928 20043 19053 2008 17863 19916 20074 20979 20625 19509 19413 19596 18739 18217 18077 2009 17494 19083 19031 19460 20734 19856 19078 18940 19261