Back to forecast
What is Lake-Effect Snow?
December 1, 2025 at 03:31 PM EST
By WeatherBug Meteorologist, Mark Paquette
Lake-effect snow is a cold season meteorological phenomenon that occurs in certain areas of the world near very large bodies of water, most famously downwind of the Great Lakes in North America.
This occurs when cold air masses move over warmer lake waters, picking up moisture and heat from the water's surface. As the warmer, moister air rises and encounters the much colder air aloft, it cools and condenses, forming abundant clouds and eventually leading to heavy snowfall.
Several important factors contribute to the development of lake-effect snow are as follows:
Temperature Difference: The temperature difference between the cold air mass heading over the lake and the relatively warmer lake water is crucial. The larger the difference between the two, the more potential there is for significant and debilitating lake-effect snow. This is exactly the reason why some of the biggest lake-effect events of the season occur early on in the cold season when the lake is still holding onto some of the warmth from the previous summer and autumn.
Wind Direction: A constant wind direction is important for sustained lake-effect snow. When the wind blows across the lake for an extended period, it allows the atmosphere to pick up moisture consistently. It will also allow for the snow to be put down in a specific area. For example, Buffalo, N.Y., sees its heaviest lake-effect snow when the wind is west-southwest as it lines best up with the orientation of Lake Erie. If the wind is from the northwest, the city won't see the bands set up near or over them.
Fetch: The distance the wind travels over the lake is called the fetch. The longer the fetch is, the more moisture the atmosphere is able to acquire, leading to heavier snowfall.
Lake Size: In general, larger lakes generally produce more intense and widespread lake-effect snow because they have more surface area to contribute moisture to the air.
Lake-effect snow is most common during the late fall and early winter when the air temperature over the lakes is still relatively warm while the air temperature over the land is colder. However, lake-effect snow is possible whenever a very cold air mass travels over bodies of water at any point in the cold season, even if the lake is frozen or partially frozen. The snowfall from lake-effect snow can be blindingly intense and very localized, leading to significant and heavy accumulations for specific areas downwind of the lakes. Often times, the same places get hit with lake-effect year after year because of similar winds and other meteorological conditions repeating themselves. This phenomenon can have a major impact on the local weather and can result in tremendously heavy snowfall and rapid changes in visibility resulting in major travel headaches.
(Image courtesy of Michael Jarmoluk from Pixabay.com)
This occurs when cold air masses move over warmer lake waters, picking up moisture and heat from the water's surface. As the warmer, moister air rises and encounters the much colder air aloft, it cools and condenses, forming abundant clouds and eventually leading to heavy snowfall.
Several important factors contribute to the development of lake-effect snow are as follows:
Temperature Difference: The temperature difference between the cold air mass heading over the lake and the relatively warmer lake water is crucial. The larger the difference between the two, the more potential there is for significant and debilitating lake-effect snow. This is exactly the reason why some of the biggest lake-effect events of the season occur early on in the cold season when the lake is still holding onto some of the warmth from the previous summer and autumn.
Wind Direction: A constant wind direction is important for sustained lake-effect snow. When the wind blows across the lake for an extended period, it allows the atmosphere to pick up moisture consistently. It will also allow for the snow to be put down in a specific area. For example, Buffalo, N.Y., sees its heaviest lake-effect snow when the wind is west-southwest as it lines best up with the orientation of Lake Erie. If the wind is from the northwest, the city won't see the bands set up near or over them.
Fetch: The distance the wind travels over the lake is called the fetch. The longer the fetch is, the more moisture the atmosphere is able to acquire, leading to heavier snowfall.
Lake Size: In general, larger lakes generally produce more intense and widespread lake-effect snow because they have more surface area to contribute moisture to the air.
Lake-effect snow is most common during the late fall and early winter when the air temperature over the lakes is still relatively warm while the air temperature over the land is colder. However, lake-effect snow is possible whenever a very cold air mass travels over bodies of water at any point in the cold season, even if the lake is frozen or partially frozen. The snowfall from lake-effect snow can be blindingly intense and very localized, leading to significant and heavy accumulations for specific areas downwind of the lakes. Often times, the same places get hit with lake-effect year after year because of similar winds and other meteorological conditions repeating themselves. This phenomenon can have a major impact on the local weather and can result in tremendously heavy snowfall and rapid changes in visibility resulting in major travel headaches.
(Image courtesy of Michael Jarmoluk from Pixabay.com)