On a visible satellite image, clouds appear white, while land and oceans show up darker. But this time of year, snow on the ground will appear white as well.

There's a few ways to tell the difference between clouds and snowcover. Snow-covered land usually isn't as bright-white as clouds are. Here's an example where the Adirondack Mountains of northern New York clearly stand out. That's heavily forested land, and the snow falls from the tree tops. So a lot of brown and green is mixed with the white.

Another characteristic to look for - water bodies. Here's a view of northeastern North Carolina after a snowstorm about a week ago. The darker rivers and bays give away the presence of snow on the adjacent land. That's because when rivers and lakes aren't frozen over, the snow cover will abruptly end at their edge.

Finally, another way to see the difference - play a loop of visible satellite images; the clouds will move, but the snow cover won't.