Weather enthusiasts have long called Thundersnow the "holy grail" of meteorological events—it is the incredibly rare kind of thunderstorm with snow falling instead of rain. The last time we saw it was over two years ago—but it happened all across Long Island and other parts of NY during last night's nor'easter. And the elusive event was even captured on camera by Christine Heeren in Middle Island, NY. Watch below, and see the sky literally turn purple!

For more info about Thundersnow, you can learn more about it here and here. Or you can just watch Stephen Colbert below explain how Thundersnow is one of the Four Snowmen of the Apocalypse.