Year,Jan.,Feb.,Mar.,Apr.,May.,Jun.,Jul.,Aug.,Sep.,Oct.,Nov.,Dec.,24-Hour Annual Avg., 2001,,,,,15703,17888,17756,18583,18271,18522,18059,17534,, 2002,18135,18902,19201,20869,21110,20795,20713,21198,20749,21015,19809,19679,20181, 2003,19862,20821,20301,21406,21175,21451,21215,20512,20866,20891,18912,19592,20584, 2004,18830,19939,20970,21958,21198,21791,20758,20607,21021,20820,20380,20353,20719, 2005,19778,21269,21568,21988,21643,22235,20417,21179,20500,20433,20328,20005,20945, 2006,20198,20955,21192,21327,21993,22037,20233,21317,20555,20657,20257,19434,20846, 2007,19971,20753,21131,21666,21859,21536,20540,21546,20553,21771,20568,19571,20955, 2008,19755,20789,20442,21987,21558,20535,20219,20091,20693,21005,19807,19583,20539, 2009,19476,20515,20399,22366,21675,21523,23055,22256,20955,21216,20314,20259,21167, 2010,19695,20712,21830,22723,21780,22302,21554,21533,20591,20844,20148,20006,21143, 2011,20836,21186,21238,22091,21981,22072,21120,21616,21141,21251,20176,20288,21250, 2012,19936,20898,20939,21963,21661,21856,20654,21258,21070,21225,20494,20218,21014, 2013,19084,21017,21388,22428,22261,22384,21133,21459,21630,21612,19704,18351,21038, 2014,18777,19512,20150,20876,20349,20628,21509,21038,21514,22462,18962,19538,20443, 2015,20222,20775,20313,21099,20578,20677,19378,18278,,13039,12409,12338,,