How the meter works
Every number on this site comes from one published model. Nothing is hidden and nothing is hand-tuned per storm. If you think a term is wrong, tell us; the accuracy page reports how the model did after each storm.
1. The forecast
Hourly forecasts come from Open-Meteo, which blends the national weather models (NOAA's GFS and HRRR in the US, ECMWF globally, Environment Canada and the Met Office for Canada and the UK). We read six days of hours in your local time and refresh every 30 minutes. Active alerts for your exact coordinates come from the National Weather Service every 15 minutes.
2. The windows
- Overnight snow: 6 pm the evening before to 8 am, in inches.
- Morning snow: 4 am to 9 am, counted at half weight on top, because snow falling on the commute is what superintendents look at.
- Snow the day before: 8 am to 6 pm the previous day, counted at 35 %, for roads that were never cleared.
- Ice hours: hours of freezing rain or drizzle before 9 am, by weather code or by liquid precipitation at or below 32 °F.
- Wind chill and wind: the lowest apparent temperature between 5 am and 9 am; the highest wind before 9 am.
3. The score
Start at −3.2. Add 3.4 × (effective snow ÷ your state's threshold), capped at three thresholds. If air reaches 38 °F overnight the snow term is halved. Each ice hour adds about 1.1 (1.6 in states that close below 2 inches), capped at 3. Wind chill adds 0.7 below −15 °F, 1.8 below −25 °F, 3.2 below −35 °F. Wind over 35 mph with snow on the ground adds 0.8. The strongest active warning adds its weight: Blizzard or Ice Storm Warning 2.5, Winter Storm Warning 1.8, Extreme Cold or Wind Chill Warning 1.6, Lake Effect Snow Warning 1.6, Winter Weather Advisory 0.8, Winter Storm Watch 0.6. Colleges subtract 1.4, private schools 0.3. The score goes through a logistic curve to become the closure chance; the delay-or-closure chance is the same curve shifted by 1.3. Weekends, federal holidays and the working days between Christmas Eve and New Year's return 0 %.
4. Confidence
Tomorrow is high confidence, the day after medium, three or more days out low: snow totals in a forecast that far ahead routinely move by several inches. Check again after 9 pm the night before, when the evening model runs are in.
5. State thresholds
Inches of overnight snow at which public-school closures become common. These are model estimates from typical district practice, not official policy; mountain and lake-effect regions inside a state differ.
| State | Closes around | Note |
|---|---|---|
| Alabama | 0.5″ | Any accumulating snow or a glaze of ice closes schools; the state rarely has the plows for more. |
| Florida | 0.5″ | Snow days are close to mythical; the Panhandle closes on any wintry mix or ice. |
| Louisiana | 0.5″ | Any frozen precipitation closes schools; the 2025 Gulf snowstorm shut the state for days. |
| Mississippi | 0.5″ | Any snow or ice closes schools statewide. |
| Texas | 0.5″ | Any snow or ice closes schools, including in Dallas and Austin; the 2021 freeze is the reference. |
| Arkansas | 1″ | An inch or freezing rain is enough; ice storms are the classic Arkansas closure. |
| Georgia | 1″ | Atlanta closes on an inch or on ice, and often the night before the forecast even arrives. |
| South Carolina | 1″ | An inch, or any ice, closes schools; the Upstate sees it most. |
| Arizona | 1.5″ | Phoenix never sees it; Flagstaff and the high country close on heavy snow and closed highways. |
| North Carolina | 1.5″ | Charlotte and Raleigh close on an inch or on ice; the mountains at more. |
| Oklahoma | 1.5″ | Ice storms are the main closer; 1 to 2 inches of snow usually does it too. |
| Tennessee | 1.5″ | One to two inches or ice; many counties now switch to remote days instead. |
| California | 2″ | Only mountain and foothill districts ever close; Sierra and Shasta towns act on chain controls and road closures. |
| Kentucky | 2″ | Hilly rural bus routes mean 2 inches or any ice closes many counties; NTI days cover the rest. |
| New Mexico | 2″ | Albuquerque delays on a couple of inches; the northern mountains close on more. |
| Oregon | 2″ | Portland closes on 2 inches or freezing rain; the east side and Cascades tolerate more. |
| District of Columbia | 2.5″ | DC Public Schools close on a few inches or ice; the federal government's status often sets the tone. |
| Virginia | 2.5″ | Northern Virginia and Richmond close on 2 to 3 inches; the Shenandoah tolerates more. |
| Washington | 2.5″ | Seattle closes on 2 inches on its hills; Spokane and the east side at 6 or more. |
| Delaware | 3″ | Three inches overnight usually does it, and ice closes at less. |
| Kansas | 3″ | Ice and blowing snow do most of the closing; three to four inches overnight is usually enough. |
| Maryland | 3″ | Baltimore and the DC suburbs close on 3 inches or ice; Western Maryland tolerates more. |
| Missouri | 3″ | Three to four inches, or ice, closes St. Louis and Kansas City districts. |
| Nevada | 3″ | Reno and Carson City close on heavy Sierra snow; Las Vegas does not have the question. |
| West Virginia | 3″ | Steep bus routes close counties on 2 to 3 inches or any ice. |
| Illinois | 4″ | Chicago Public Schools close for extreme cold as often as for snow; suburbs close at 4 to 6 inches. |
| Indiana | 4″ | Four inches overnight or a wind chill warning brings closures; e-learning days replace many of them now. |
| New Jersey | 4″ | Four inches overnight, less near the coast where ice and wind are the concern. |
| Ohio | 4″ | Four inches overnight or a wind chill warning; Cleveland's snow belt tolerates more. |
| Pennsylvania | 4″ | Four inches overnight; Philadelphia closes on less, the Alleghenies on more. |
| Colorado | 5″ | Front Range districts ride out moderate snow; closures come with heavy overnight totals, wind and deep cold. |
| Connecticut | 5″ | Delays are common at 3 to 4 inches; closures at 5 or more, or whenever ice is in the mix. |
| Iowa | 5″ | Wind and drifting matter more than totals; blizzard warnings close rural districts fast. |
| Nebraska | 5″ | Blizzard conditions and wind chill close schools; five to six inches on a calm night may only delay. |
| New York | 5″ | NYC almost never closes; upstate and Long Island districts close at 5 to 8 inches, Buffalo at far more. |
| Rhode Island | 5″ | Five inches overnight, or a coastal storm with wind and ice. |
| Idaho | 6″ | Boise rarely closes; mountain districts close on heavy snow and drifting roads. |
| Maine | 6″ | Six inches overnight or ice; Mainers delay first and close when the plows cannot keep up. |
| Massachusetts | 6″ | Six inches overnight is the classic Boston closure; nor'easters with wind close on less. |
| Michigan | 6″ | Lake-effect country: 6 inches, drifting, or a wind chill warning; the Upper Peninsula tolerates more. |
| New Hampshire | 6″ | Six inches overnight; delays at four; ice storms close everything. |
| Utah | 6″ | Wasatch Front districts nearly never close; heavy canyon snow and closed roads are the exception. |
| Vermont | 6″ | Six inches overnight on a school morning; Vermont delays more often than it closes. |
| Wyoming | 6″ | Wind, drifting and closed interstates close schools; snow depth alone rarely does. |
| South Dakota | 7″ | Wind chill and blizzard conditions close schools far more than snow depth. |
| Wisconsin | 7″ | Seven inches overnight or wind chill near -35 °F; Milwaukee closes a little sooner. |
| Minnesota | 8″ | Eight inches or a wind chill near -35 °F; Minnesota closes for cold more often than for snow. |
| Montana | 8″ | Closures are rare and usually about wind chill and blowing snow, not totals. |
| North Dakota | 8″ | Blizzard warnings and wind chill, not inches, close North Dakota schools. |
| Alaska | 10″ | Anchorage closes for ice and extreme cold more than for snow; a foot overnight is a strong case. |
6. What it cannot know
Whether your district has already burned its emergency days, whether it runs e-learning instead of closing, the state of your specific bus routes, and the superintendent's mood at 4:45 am. That is why the result is a probability with reasons, never a promise.