YEAR Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual 24-hr Avg.
1991            12413
1992 11682 12696 13687 14285 14027 14774 15042 15295 15069 14422 12943 12179 13881
1993 10982 12463 13460 14069 14826 15797 16296 16571 16476 15640 14329 13945 14582
1994 13611 13886 16079 16304 16267 17230 17515 17883 17804 16578 15528 14927 16146
1995 14204 15562 16457 16762 16808 17761 17676 18194 17765 17561 16365 15461 16715
1996 13752 16358 17372 17533 17287 18412 18326 18717 16785 17503 16812 14998 16988
1997 14627 16595 17552 18010 17683 18278 18465 19880 19365 18623 18105 17200 17865
1998 16005 17598 18650 19731 19391 20386 20368 20847 20036 19543 18704 17581 19070
1999 16331 17332 19216 19421 20044 21015 21464 22108 20428 19596 19092 18176 19519
2000 16966 18640 19735 19701 20310 21501 21470 23228 22064 21543 18999 18981 20262
2001 17337 19019 20533 21313 21506 22589 22068 22939 21763 21474 20367 17992 20742
2002 17675 19602 20624 19609 19339 19272 21432 23810 23044 21859 20915 20324 20625
2003 19253 20177 20935 22098 22716 23061 22989 23770 23671 22910 20974 19897 21871
2004 18180 19400 21956 22843 22169 23232 23154 23782 23355 22248 21459 20681 21872
2005 18803 20900 22003 22839 22036 23262 23736 24738 22981 22082 21266 20512 22097
2006 19033 20049 19443 22399 22330 22967 22251 22492 21828 22380 21507 20745 21452
2007 19394 20180 23332 23966 22222   23553 23219 22747 22329 19894
2008 18909 20294 21741 22699 22473 22718 22831 22623 23091 22437 21115 19430 21697
2009 19559
2010 
2011    22661 22548 23526 23487 24274 23640 23024