Lake-effect snow and school closings

Cold air crosses a warm lake and drops a narrow band of heavy snow on the shore downwind. One school district gets a foot; the next gets flurries.

By Petar M., editor · Updated October 18, 2026 · How we research

In this guide (5)

How lake-effect snow forms
Why it hits one town and not the next
The snowbelt: much more snow, and more needed to close
Big lake-effect storms
Lake-effect nights and the calculator

How lake-effect snow forms

In late fall and winter, cold air, often from Canada, blows across the open water of the Great Lakes, which is still much warmer than the air. The lake warms and moistens the bottom of the air mass, clouds grow quickly, and they drop their snow when they reach land on the downwind shore.

A common rule of thumb used by NWS forecasters: lake-effect snow forms when the lake surface is about 13°C (23°F) warmer than the air about a mile up. The longer the stretch of water the wind crosses, the heavier the snow.

Why it hits one town and not the next

Lake-effect snow falls in narrow bands. The NWS describes bands that can produce 2 to 3 inches of snow an hour or more, while the sun shines a mile or two away. A small change in wind direction moves the band north or south, so totals change sharply over short distances.

For schools, that means neighboring districts can face completely different mornings, and a regional forecast of "6 to 12 inches" may mean 2 inches for one district and 20 for another. The calculator reads the forecast for each ZIP code on a grid about 2.5 km (1.5 miles) wide, which helps with banded snow, but the exact position of a band is still one of the hardest things to forecast.

The snowbelt: much more snow, and more needed to close

The places downwind of the lakes, such as the Tug Hill Plateau east of Lake Ontario and the shores south and east of Lakes Erie and Michigan, get far more snow than cities upwind. Districts there handle snow every week, so it takes much more to close them:

City	Position	Snow a year	Snow that usually closes schools (model)
Syracuse, NY	east of Lake Ontario	128 in.	about 13 in.
Erie, PA	south shore of Lake Erie	104 in.	about 12 in.
Rochester, NY	south shore of Lake Ontario	102 in.	about 11 in.
Buffalo, NY	east end of Lake Erie	95 in.	about 11 in.
Grand Rapids, MI	east of Lake Michigan	75 in.	about 10 in.
Cleveland, OH	south shore of Lake Erie	64 in.	about 9 in.
Toledo, OH	west end of Lake Erie (mostly upwind)	37 in.	about 7 in.
Detroit, MI	inland, upwind of the big lakes	31 in.	about 7 in.
Milwaukee, WI	west shore of Lake Michigan (upwind)	40 in.	about 8 in.
Chicago, IL	southwest shore of Lake Michigan (upwind)	39 in.	about 7 in.

NOAA NCEI 1991–2020 normals at each city's nearest station. The closing line is our model's estimate, not a district policy.

Big lake-effect storms

Buffalo, November 2014. Two lake-effect storms buried the Buffalo Southtowns; one spot in South Cheektowaga measured 65 inches from the first, and totals from the two storms reached nearly 7 feet, with snowfall rates near 6 inches an hour (NWS Buffalo).
Buffalo, November 2022. Several places in the Boston Hills and the Buffalo Southtowns totaled 5 feet or more (NWS Buffalo).
New York's 24-hour record is 50 inches at Camden in 1966, on the Tug Hill side of Lake Ontario (NOAA's State Climate Extremes Committee). A widely reported 77 inches at Montague in January 1997 was not accepted as an official 24-hour total.

Lake-effect nights and the calculator

Watch for a Lake Effect Snow Warning (or a Winter Storm Warning in regions that don't use it). The calculator raises the chance for either.
Check your own ZIP, not the nearest city. A band can sit over one suburb all night and miss the city center.
Look at the hours. Bands often set up overnight and drift by morning; the snow-by-hour chart on the result shows whether the heaviest snow falls before buses run.

Check your district

See tomorrow's chance of a closure or delay for your ZIP code. Open the calculator, or find your state or city.