Lake effect snow and snow squalls
Lake effect snow forms when cold air crosses the warmer Great Lakes and builds narrow bands that can drop 2 to 3 inches an hour or more. Conditions change within a mile or two. If a Lake Effect Snow Warning or Snow Squall Warning is out, delay travel if you can, and if you're already driving, slow down with your headlights and hazards on.
Information may be delayed or incomplete. Always verify with official sources and follow local officials.
What is lake effect snow?
“Lake effect snow is common across the Great Lakes region during the late fall and winter.”National Weather Service, What is a Lake Effect Snow?
The National Weather Service says it starts when cold air, often from Canada, moves across the open, unfrozen water of the Great Lakes. The lake water is warmer than the air, so warmth and moisture rise into the lowest part of the atmosphere. Clouds form and grow into narrow bands of snow.
“The air rises, clouds form and grow into narrow band that produces 2 to 3 inches of snow per hour or more.”National Weather Service, What is a Lake Effect Snow?
Why one town gets buried and the next stays sunny
Lake effect snow falls in narrow bands, so totals can change fast over a short distance. The National Weather Service says heavy snow may be falling in one place while the sun shines just a mile or two away. Wind direction decides which areas get the bands, and the shape of the land and shoreline matters too (NWS: Lake effect snow).
That means a forecast for your county can look very different from what you see out the window, and the band can shift as the wind changes. Check your local NWS forecast and alerts before you head out, not just the morning outlook.
What the alerts mean
Your local National Weather Service office issues these, and the snow amounts behind them vary by area (NWS: Winter warnings, watches and advisories):
- Lake Effect Snow Warning: lake effect bands are expected to bring significant snow. The NWS says these bands can produce very heavy snow with sudden drops in visibility, and driving may become hazardous.
- Lake Effect Snow Advisory: lake effect snow below warning levels. Expect snow showers and assume travel will be difficult in some areas.
- Snow Squall Warning: a short, intense burst of snow and wind is moving through. These warnings are short-fused and cover small areas, like tornado warnings (NWS: Snow squalls).
Snow squalls on the road
“The sudden white-out conditions combined with falling temperatures produce icy roads in just a few minutes.”National Weather Service, Snow Squall
The National Weather Service says snow squalls usually last 30 to 60 minutes and often drop an inch of snow or less, but the mix of gusty wind, falling temperatures and sudden white-outs has led to deadly crashes.
- Delay the trip. If a Snow Squall Warning is out for your area, the NWS says to avoid or delay driving until the squall passes.
- If you're already driving, slow down, turn on your headlights and hazard lights, and leave plenty of room between you and the car ahead (NWS).
- Don't slam on the brakes. On slick roads, the NWS says that can cause you to lose control and set off a chain-reaction crash.
- Check before you start the car. Look up the latest warnings on weather.gov before you leave.
“There truly is no safe place on the highway during a snow squall.”National Weather Service, Snow Squall
Getting ready for lake effect season
- Keep a winter kit in your car: blankets, a phone charger, a flashlight, water, snacks, a shovel, an ice scraper and sand or cat litter. See our winter driving guide for the full list.
- Keep your gas tank over half full (NWS) and tell someone your route when the bands are active.
- Have supplies at home. Ready.gov says to gather supplies in case you need to stay home for several days without power, including each person's medicine, your pets' needs and extra batteries (Ready.gov: Winter weather).
- Pace yourself shoveling. Ready.gov says to avoid overexertion when shoveling snow to reduce the risk of a heart attack.
- If the power goes out, Ready.gov says to use generators only outdoors, at least 20 feet from windows, doors and attached garages. See Winter outages, generators and frozen pipes.
Common questions
What is lake effect snow?
The National Weather Service says it forms when cold air, often from Canada, moves over the unfrozen and relatively warm Great Lakes. The air picks up warmth and moisture, rises, and builds narrow bands of snow that can drop 2 to 3 inches an hour or more.
Why is it snowing hard here but sunny a few miles away?
Lake effect snow falls in narrow bands. The National Weather Service says heavy snow can fall in one spot while the sun shines a mile or two away, and wind direction decides where the bands set up.
What is a Lake Effect Snow Warning?
The National Weather Service issues one when lake effect snow bands are expected to bring significant snowfall. The bands can cause very heavy snow and sudden drops in visibility, and driving can become hazardous. A Lake Effect Snow Advisory is for snow below warning levels.
What should I do if a snow squall hits while I'm driving?
Get off the road if you can. If you can't, the National Weather Service says to slow down, turn on your headlights and hazard lights, leave plenty of space, and avoid slamming on the brakes.
Is shoveling heavy lake effect snow risky?
It can be. Ready.gov says to avoid overexertion when shoveling snow to reduce the risk of a heart attack. Take breaks and don't push past your limits.
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