All I can say is that 'weather is weather'. (that "global warming" is, indeed, hype has been my position from the get-go) I'm sure that somewere within the miniscule time that accurate weather records have been kept, snow was recorded in mid May for your area.
My Dad emailed me this morning from Wallaceburg, Ontario reporting the snow. My response is that it is still Spring there, isn't it.
As my seasons are opposite to yours (it's now late Autumn), I can report that I was outside working comfortably in a tee-shirt with the temperature at 21C. Adelaide, SA, just had their warmest weekend in 92 years (31C)... but that's the point, it has happened before.
Right now it's back to Autumn with heaps of rain & the temps to return to morning frosts. :confused3: