YEAR Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual 24-hr Avg. 1990 14203 14947 16112 16082 16099 16505 15895 16452 14861 15177 15885 17791 15841 1991 13644 14897 15528 15819 16270 16344 16367 14811 11701 13929 15614 17293 15191 1992 14601 15555 15796 16452 16366 16128 16242 16468 15692 15950 15707 17761 16107 1993 14402 15547 16407 16830 17019 17472 17530 17635 17013 17280 17213 19174 16970 1994 16224 17522 17691 17670 17816 18363 18368 18734 17519 17812 18023 20114 17993 1995 13784 18347 17429 18348 17523 17823 18632 20443 1996 16748 18390 18535 18554 18751 19042 18240 18745 18169 17882 18237 19386 18390 1997 16383 17643 17943 18180 18587 18734 18510 18849 17669 18123 18545 20377 18295 1998 17395 18143 18740 18913 19496 19671 19380 19811 18635 19044 19274 20837 19112 1999 17860 18771 19233 19648 20166 20498 20026 20303 19435 19639 19575 21153 19692 2000 17815 18993 19110 19489 19539 19988 20795 22736 21006 19970 19669 21091 20017 2001 17768 18736 19339 18728 19127 19553 19572 19892 18397 18446 19251 20043 19071 2002 17382 18405 18799 18625 18874 18412 18475 19479 17842 18246 18798 20137 18623 2003 17478 17567 16711 17336 17889 17916 17423 17715 17410 18906 18733 20170 17938 2004 17884 18029 19089 19249 18855 19360 19326 19121 17731 18075 18433 20416 18797 2005 16814 18249 18310 18507 18786 19036 18910 19416 17433 17549 17980 20192 18432 2006 17094 18137 18792 19167 19520 19818 19257 19243 18103 18903 19791 21464 19107 2007 18384 19591 20401 20194 20754 20863 20553 21444 20048 20436 20612 21741 20418 2008 18797 20076 20460 21189 21959 21689 21333 21244 20319 21445 21790 22746 21087 2009 20464 21489 21279 23179 23439 22249 22141 22112 20693 22371 21284 23046 21979 2010 20086 21510 21644 23974 21452 22187 21317 21516 20523 21053 20560 23063 21574 2011 19924 20985 21178 21674 22192 23240 20850 22481 21003 21416