Ice storms and school closings
Snow can be plowed. Ice can't, not quickly. That is why a thin glaze of freezing rain shuts down districts that would open in several inches of snow.
By Petar M., editor · Updated October 18, 2026 · How we research
In this guide (5)
What makes ice different
Freezing rain falls as liquid and freezes on contact with roads, trees and power lines that are below freezing. The result is a clear coat of ice that tires can't grip and plows can't push. Salt helps, but slowly, and much less in very cold air. Bridges, overpasses and shaded roads ice over first.
- Buses can't stop. Even a few hundredths of an inch makes hills and intersections dangerous.
- Power goes out. Heavier ice brings down branches and lines, and a school without power or heat can't open.
- It's hard to see. "Black ice" looks like wet pavement, so drivers don't slow down.
How much ice closes schools
Far less than snow, almost everywhere. Our model treats roughly a tenth of an inch of ice accretion overnight as enough to make a closure likely, a little more in places used to winter driving:
| City | Days a year with 3+ in. of snow | Ice that usually closes schools (model) |
|---|---|---|
| Atlanta, GA | 0.0 | about 0.12 in. |
| Dallas, TX | 0.1 | about 0.13 in. |
| Nashville, TN | 0.1 | about 0.13 in. |
| Charlotte, NC | 0.3 | about 0.14 in. |
| Washington, DC | 1.3 | about 0.15 in. |
| Philadelphia, PA | 2.0 | about 0.16 in. |
| Chicago, IL | 3.6 | about 0.18 in. |
| Buffalo, NY | 9.1 | about 0.21 in. |
Ice line from our model (0.12 in. plus a small allowance for snowy climates). Snow days: NOAA NCEI 1991–2020 normals. Not a district policy.
A storm with a little snow and a little ice scores higher than either alone: the calculator adds part of the second hazard to the first.
The NWS ice alerts
- Ice Storm Warning: damaging ice accretion is expected; the amount that triggers it is set by each local NWS office, often around a quarter inch.
- Winter Storm Warning or Winter Weather Advisory: often issued for mixed snow, sleet and freezing rain, or for lighter icing.
When an Ice Storm Warning covers your county, the calculator raises the chance of a closure the most of any alert, along with a Blizzard Warning.
Sleet vs. freezing rain
Sleet is ice pellets that bounce and pile up, more like gritty snow; it is slippery but plowable. Freezing rain glazes everything. Forecasts often show both in the same storm, and the line between them can move a few miles in an hour, which is why ice forecasts are so uncertain.
What to watch the night before
- Temperatures near or just below 32°F at the ground, with warmer air above (the classic freezing-rain setup).
- Ice in the forecast between midnight and 8 AM.
- An Ice Storm Warning or a Winter Weather Advisory mentioning freezing rain.
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.
Sources
- National Weather Service, winter weather warnings and advisories
- National Weather Service, ice storms (winter safety)
- Snow Day Calculator, how it works