Snow Day Calculator

Estimate the odds of a school closure or delay from forecast snowfall, timing, temperature, ice, wind and how used to snow your region is.

A transparent heuristic estimate, not an official announcement.

Last updatedHow we build & check our tools
in
F
mph
Results will appear here once you enter your values.

This is an estimate, not an announcement

The percentages come from a simple scoring model, not from your school district. No calculator knows how fast your county's plows run, whether a bus route climbs a shaded hill, or whether the superintendent already drove the roads at 4:30 a.m. Treat the number as a for-fun, entertainment-only way to think through the forecast, not as a decision.

The only source that counts is your district: its website, text or email alerts, app, or official social media accounts, plus local TV and radio closing lists. Many districts announce by 5:30 to 6:00 a.m., and some decide the night before when ice is expected.

How the score is built

Each factor adds or subtracts log-odds points, and the total z becomes a probability with the logistic curve p = 1 / (1 + e^(-z)), capped at 99% because nothing is certain. The weights are fixed and visible, so the same inputs always give the same answer, and more snow, more ice, colder air or stronger wind can never lower the odds.

  • Base: -0.6.
  • Snow vs region: 2.5 x ln((snow + 0.25) / (threshold + 0.25)), never below -4. Thresholds are 1 in for the South, 3 in for the Mid-Atlantic, 6 in for the Midwest and Northeast, and 8 in for the Snow Belt and mountains.
  • Timing: overnight into the commute +1.0, during the school day -0.8 (early dismissal is more common), evening ending by midnight -1.0, weekend returns 0%.
  • Overnight low: 32 F or warmer -0.5, 25 to 31 F 0, 15 to 24 F +0.3, 0 to 14 F +0.7, below 0 F +1.3.
  • Ice: trace +2.0, 0.1 in or more +4.5.
  • Wind with at least 1 in of snow: 25 to 34 mph +0.5, 35 mph or more +1.0.
  • School type: private -0.3, college -1.5.

Worked examples

A Midwest district expecting 6 in overnight with a low of 22 F scores -0.6 + 0 + 1.0 + 0.3 = 0.7, about a 67% closure chance. The same 6 in falling during the day drops to 25%, because districts usually send students home early instead of closing the next day once roads are treated.

In the South, 2 in overnight at 28 F scores -0.6 + 1.47 + 1.0 = 1.87, about 87%, because many Southern counties have a handful of plows and buses cannot handle hills. A Snow Belt district with 3 in overnight at 20 F scores only -1.63, about 16%, and a delay is the more likely outcome. An ice storm with 0.1 in of glaze and no snow in the Mid-Atlantic still reaches about 71%.

Why ice and cold matter so much

The National Weather Service notes that even a thin glaze of freezing rain makes roads and sidewalks treacherous, and many NWS offices issue ice storm warnings at a quarter inch of ice, enough to bring down power lines and tree limbs. Salt loses effectiveness as pavement temperatures fall, so a storm followed by single-digit lows leaves roads icier at 7 a.m. than the snow total suggests.

Extreme cold closes schools on its own in the northern Plains and upper Midwest. With an air temperature of 0 F and a 15 mph wind, the NWS wind chill chart gives -19 F, where frostbite can develop in about 30 minutes, which is why students waiting at bus stops drive many cold-day decisions.

Frequently Asked Questions

Common questions about the Snow Day Calculator

No. It is a heuristic estimate built from general rules of thumb. Only your school district can announce a closure or delay, so check its website, alerts or local news. It is meant for fun and entertainment.

Sources & References

Winter Weather Safety

NWS guidance on winter storm hazards, watches and warnings.
→Source: National Weather Service

Ice and Frost Safety

How freezing rain and ice accumulations affect travel and power.
→Source: National Weather Service

Wind Chill Chart

Wind chill values and frostbite times used to explain cold-day closures.
→Source: National Weather Service

Winter Storm Severity Index

NOAA's official product for gauging the expected societal impact of winter storms.
→Source: NOAA Weather Prediction Center

Explore More Tools

Explore these related tools for your next step.

climate

Mulch Calculator

Calculate how much mulch you need in cubic yards, cubic feet and bags for one or more rectangular, circular or measured beds. Includes depth guidance and optional bulk or bagged cost.

Try it now
climate

Plant Hardiness Zone Finder

Find your USDA plant hardiness zone by ZIP code using the official 2023 USDA map data, or from your area's average annual extreme minimum temperature.

Try it now
climate

Enhanced Fujita Scale Calculator

Convert an estimated tornado wind speed in mph, km/h or m/s to an EF rating, compare it with the original Fujita scale, and look up the wind range for any EF level.

Try it now
climate

Topsoil Calculator

Estimate how much topsoil to order in cubic yards, bags and tons for a new lawn, a topdressing or a garden bed. Includes a settling allowance and an editable soil density.

Try it now
climate

Raised Bed Soil Calculator

Work out how much soil fills your raised beds in cubic feet, cubic yards and bags, then split the total into ingredients for a 60/30/10, Mel's Mix or 50/50 recipe.

Try it now
climate

VPD Calculator (Vapor Pressure Deficit)

Calculate leaf and air vapor pressure deficit from air temperature, relative humidity and leaf temperature, with a color-banded VPD chart for propagation, vegetative and flowering stages.

Try it now