I still can't believe this actually happened... Heavy rain changed to heavy thundersnow and thundersleet mixed w/ graupel as far south as Moncure, Clayton, and Wilson in early May 1939, and snow managed to accumulate in Roxboro, Oxford, and Henderson in the middle of the day near high noon w/ a sun angle and insolation equivalent to what we see in August. So much for that sun angle and warm ground temps precluding accumulation.

The big takeaway here (as we've also seen in other storms this year) ground temps, sun angle, etc. are pretty irrelevant if the precipitation is heavy enough and you're encased w/ thick cloud cover.
View attachment 4980