Rain in May

Everyone seems surprised at the recent rain. I know that I was. There is a definite chance of rainfall in May - the median rainfall amount is 0.02" in Los Angeles and the third quartile is 0.11" (meaning that statistically speaking there's a 75% chance of up to 0.11").

In fact, since 2000, we've had measurable May rainfall in 9 of 11 years.

2009 0.00"
2008 0.12
2007 0.36
2006 0.62
2005 0.34
2004 0.04
2003 0.98
2002 0.12
2001 0.04
2000 0.00

1998 and 1977 had about 2 inches of rain in May! However, as I look over the May rainfall figures it seems that there are quite a few more 0.00's in years prior to 2000 than in years subsequent to it. The following graph shows a moving average of May rainfall and it appears that we're actually in an increasing trend. There are are decade-long or longer trends in weather, but one can always hypothesize global warming as the culprit. 

Or it could just be the weather.