Thunder snow
Outside the window it has just dumped half an inch of snow with thunder and lightning - I have never seen the combination before.
So I looked it up to see how rare it was:
Answer to "thunder and snow" question
Thunderstorms usually require warm, humid air near the ground (where we hang out) to form. Warm air rises, cools, the moisture in the air condenses, and this can lead to the development of thunderstorms.
Obviously in a winter storm / blizzard that is not the case.
However, the air near the ground can be "relatively" warm compared to the air at high altitudes. In this case, thunderstorms (usually relatively weak and short-lived) can develop. And, under some circumstances, many such storms can develop.
"For a more detailed answer, see The New York Times Learning Network's Thunder Snow. For a more technical explanation, see the NOAA/National Severe Storms Laboratory's paper titled, Thunderstorms observed at surface temperatures below freezing across North America."
