Definition

Lake Effect Snow is a heavy, localized snowfall in the proximity of large bodies of open water occurring when a cold air mass and accompanying winds move over warmer lake water. Lake effect snow clouds normally form in narrow bands, referred to as "streamers" which can be as much as 40 km wide and extend over 100 km inland from the lake. Within the streamer, snowfall rates can exceed 15 cm per hour.

Lake effect snow is prevalent in the Great Lakes region of North America but also occurs in several other areas.