| North | Pacific | |||
| Year | Spring | Summer | Fall | Winter |
| 1999 | 0.7 | 0.6 | 1.3 | 0.6 |
| 2000 | 0.9 | 0.9 | 0.5 | 0.6 |
| 2001 | 0.8 | 0.81 | 1 | 0.9 |
| 2002 | 0.9 | 1.3 | 1.2 | 1.1 |
| 2003 | 1.2 | 1 | 1 | 1.1 |
| 2004 | 1.2 | 1.5 | 1.3 | 1.3 |
| 2005 | 1.1 | 1.1 | 1.1 | 1.7 |
| 2006 | 1.2 | 1.3 | 1.3 | 1.1 |
| 2007 | 1.2 | 1.1 | 0.9 | 1.2 |
| 2008 | 1.1 | 1.3 | 1.4 | 0.9 |
| 2009 | 0.4 | 0.3 | 0.3 | 0.4 |
| 2010 | 0.3 | 0.4 | 0.4 | 0.3 |
| 2011 | 0.4 | 0.5 | 0.4 | 0.5 |
| 2012 | 0.5 | 0.5 | 0.5 | 0.3 |
| 2013 | 0.6 | 0.5 | 1.1 | 1.5 |
| 2014 | 1.8 | 1.5 | 1.6 | 1.6 |
| 2015 | 1.7 | 1.4 | 1.3 | 1.5 |
| 2016 | 1.7 | 1.5 | 1.6 | 1.6 |
| 2017 | 1.5 | 1.6 | 1.5 | 1.1 |