So why are snow thunderstorms so rare? I researched a bit and it said that it is because there is less moisture in the air. But the percentage of thunderstorms while raining seems much higher than the the percentage of thunderstorms while snowing. Less moisture would only prove why there are less snowstorms correct?
Thunder is a manifestation of lightning, the sudden discharge of (static) electrical potential between cloud and ground, or cloud and cloud. That potential is built up through convection of vapor from low to high altitudes, typically tens of thousands of feet. Though possible in winter, though unusual, this kind of convection occurs mostly during summer months when extended sunshine bakes the earth surface, causing upward atmospheric movement of anything above.