Possible PIOMAS September average based on previous years:
2000 4,314
2001 4,256
2002 4,278
2003 4,255
2004 4,300
2005 4,159
2006 4,110
2007 4,223
2008 3,894
2009 4,139
2010 4,257
2011 4,202
2012 4,174
2013 4,257
2014 4,126
2015 4,218
2016 4,203
2017 4,324
2018 4,217
2019 4,347