According to Weather Underground snow at the end of may isn't that rare used to happen a lot in the 1800s.
It should be noted that June snowfall in the Northeast is not a unique event to 1816. On June 11, 1842 widespread snow fell over northern New York and New England and snowflakes were observed in Cleveland, Ohio; Boston, Massachusetts; and even Harrisburg, Pennsylvania (all low elevation sites). Accumulations of 10-12” were common in Vermont, so the June 1842 event was actually more extreme than the more famous snow of June 1816.So with all that carbon and methane in the air how can there be snow on Memorial Day weekend? Just as the Hoaxers were wrong to blame the tornadoes on global warming, I would be wrong to blame the snow storm on the fact that global temperatures haven't risen in almost two decades.
Other late May snowfalls in the Northeast and New York State
On May 25th, 1838 snow accumulated 6-8” at Otisco, New York, Onondaga County (elev. 1,460’) and Bradford, Pennsylvania picked up 10”. Pittsburg also reported measurable snow as did Wheeling, West Virginia. Snowflakes were observed in lower Manhattan on May 25, 1845 and in Harlem “snow also fell in quantity”. One inch accumulated in Jamaica, Queens County.
Fact is temperatures rise and fall it has nothing to do with the CO2 and greenhouse gasses in the atmosphere, but it is a product of global cycles and solar activity on man has little influence. Snow in May is just one more example those natural cycles.