Here are the last 10 years for the number of days with measureable precipitation during the equivalent forecasting time:

year	Number of Days
2017	12
2016	11
2015	10
2014	8
2013	13
2012	15
2011	21
2010	25
2009	6
2008	16

What is the probablity of getting 0 events? (Note can't use possion statistics)

Average = 13.7 days per period; standard deviation = 5.7 = 2.4 σ or 1%

But 2010 was an anamolous year, through that out and you get 12.5 +/- 4.4 or 2.85 σ or 1 in 500.

year	May inches
2017	1.25
2016	1.34
2015	0.94
2014	1.66
2013	2.04
2012	2.7
2011	2.72
2010	3.78 (Late May)
2009	3.07 (early May)
2008	0.6

May 2018 = 0.44 inches (all in early May)

Look around and you will see lawns starting to dry up, as if it was mid August.