How Rare is May Snow in Cleveland?

Sunday marked only the 12th time since the late 1800s we have had measurable snow in May.  The latest report of snow at a National Weather Service reporting station in Cleveland was May 27, 1907 when we had a trace. Keep in mind that weather reports were recorded at different location around downtown Cleveland from 1870 through the 1930s.  Readings started at Hopkins Airport southwest of the city in the mid 1920s.  

Snow cover in Middlefield, Ohio

It wasn't until the late 1930s when records became consistent and searchable. Officially, we only had a trace at Hopkins Sunday.  850 mB temps were between -5 and -7 early Sunday morning with surface tempertures in the mid to upper 30s.   The rare instances of May snowfall is list below. 

All May snowfall instances recorded at Hopkins Airport (post 1938) and downtown Cleveland 1870 to the late 1930s