Satellite image of lake-effect snow occurring over the Great Lakes region. Lake-effect snow occurs when cold dry air passes over a large, warm lake and picks up moisture and heat. Clouds build overhead and eventually develop into snow showers as they move downwind. In this image, the wind is moving from the northwest to the southeast. It picks up moisture from Lakes Nipigon, Superior, and Michigan and deposits it as snow further downwind.
Image credit: SeaWiFS Project, NASA. Public domain, via Wikimedia Commons.