Lake-effect rain

Lake-effect rain, or bay-effect rain, is the liquid equivalent of lake-effect snow, where the rising air results in a transfer of warm air and moisture from a lake into the predominant colder air, resulting in a fast buildup of clouds and rainfall downwind of the lake. If the air temperature is not low enough to keep the precipitation frozen, it falls as a lake-effect rain. In order for lake-effect rain to form, the air moving across the lake must be significantly cooler than the air over the water surface.

The resulting rain bands can accumulate to can cause localized flash flooding, thunder, lightning and even waterspouts in extreme events. Although the effect is associated with the North American Great Lakes, it can occur downwind of any large lake that can hold its summer heat well into the cooler days of autumn and early winter. Another similar effect is sea-effect or ocean-effect rain, which is caused by three primary components: a cold air mass over land, warm ocean water, and enough wind from the right direction.