Snow Day Calculator – to Predict School Closures

This Snow Day Calculator is designed to predict the probability of school closures due to winter weather conditions. These sophisticated calculators analyze various weather metrics—including snowfall amounts, temperature, wind speed, and other factors—to generate a percentage likelihood that schools will close.

Fourteen-year-old Sarah checks the weather forecast for tomorrow, which predicts 6 inches of snow overnight with temperatures around 25°F and wind speeds of 18 mph. Rather than just hoping for a day off, she uses the Snow Day Calculator to get an objective assessment. She enters her location, the weather forecast details, and selects that her district “sometimes closes” for snow. The calculator reports a 76% chance of a snow day. Sarah decides to complete her homework just in case, but also prepares her sled for a potential day of winter fun.

Snow Day Predictor Formula

The snow day prediction formula combines multiple weighted factors to calculate the probability of school closures during winter weather events.

Snow Day Probability = (Weather Severity × 0.5) + (District History × 0.3) + (Day of Week × 0.1) + (Storm Timing × 0.1)

Let’s break down each component:

• Weather Severity (50% weight): This factor combines snowfall amount, temperature, and wind speed:
  • Snowfall: Minimal (0-2″) = 0.1, Light (2-4″) = 0.3, Moderate (4-7″) = 0.4, Heavy (7″+) = 0.5
  • Temperature: Above freezing (>32°F) = 0.1, Cold (25-32°F) = 0.2, Very cold (<25°F) = 0.3
  • Wind: Light (<10 mph) = 0.05, Moderate (10-20 mph) = 0.1, Strong (>20 mph) = 0.2
• District History (30% weight):
  • Rarely closes = 0.2
  • Sometimes closes = 0.5
  • Often closes = 0.8
• Day of Week (10% weight):
  • Monday/Friday = 0.7 (schools close more easily)
  • Tuesday-Thursday = 0.4
• Storm Timing (10% weight):
  • Overnight = 0.8 (higher chance of closure)
  • During day = 0.3

Example Calculation:

• Forecast: 5″ snow, 24°F, 22 mph winds
• District history: Sometimes closes
• Day: Monday
• Timing: Overnight storm

Weather Severity = 0.4 (moderate snow) + 0.3 (very cold) + 0.2 (strong wind) = 0.9 (capped at 1.0) Snow Day Probability = (0.9 × 0.5) + (0.5 × 0.3) + (0.7 × 0.1) + (0.8 × 0.1) = 0.45 + 0.15 + 0.07 + 0.08 = 0.75 or 75%

How to Find Out Will There Be a Snow Day Tomorrow

To determine if your school will have a snow day tomorrow, follow these steps for the most accurate prediction:

• Enter the expected snowfall amount in inches based on the latest forecast for your area. Be sure to use the most accurate forecast for your specific location, not just the general metropolitan area.
• Input the predicted lowest temperature (in °F) expected during the snow event. This is crucial as colder temperatures typically mean drier, fluffier snow and icier roads.
• Add the highest forecasted wind speed (in mph) during the storm period. Higher winds create dangerous wind chill, drift snow across roads, and increase the likelihood of power outages.
• Select your school district’s closure history from the dropdown menu:
  • “Rarely Closes” for districts that typically stay open during minor snow events
  • “Sometimes Closes” for average districts with occasional snow days
  • “Often Closes” for districts that prioritize safety with more frequent closures
• Choose the day of the week the snow is expected (Monday/Friday or Tuesday-Thursday), as this impacts administrative decisions.
• Indicate when the storm will occur (overnight before school or during the school day), as timing significantly affects closure decisions.
• Click “Calculate Snow Day Probability” to generate your prediction.

The calculator will instantly display a color-coded probability percentage (red for low chance, orange for moderate chance, green for high chance) along with detailed factor breakdowns showing exactly how each element contributes to the final prediction.

What is a Snow Day?

A snow day is an unplanned school closure due to winter weather conditions that make it unsafe for students and staff to travel to educational facilities. School administrators declare snow days when weather creates hazardous transportation conditions, risks to student safety, or makes school facilities inoperable (such as when power outages or heating system failures occur).

Snow Day Probability Example Calculations

Example 1: Light Snowfall in a Conservative District

• Weather data: 2.5 inches of snow, 30°F, 12 mph winds
• District: Rarely closes (tough district)
• Day: Wednesday
• Storm timing: During school day
• Calculation:
  • Weather Severity: 0.3 (light snow) + 0.2 (cold) + 0.1 (moderate wind) = 0.6
  • District Factor: 0.2 (rarely closes)
  • Day Factor: 0.4 (mid-week)
  • Timing Factor: 0.3 (during day)
  • Probability = (0.6 × 0.5) + (0.2 × 0.3) + (0.4 × 0.1) + (0.3 × 0.1) = 0.3 + 0.06 + 0.04 + 0.03 = 43%
  • Result: Moderate chance of a snow day

Example 2: Major Storm in a Snow-Sensitive Area

• Weather data: 9 inches of snow, 18°F, 25 mph winds
• District: Often closes (snow-sensitive)
• Day: Friday
• Storm timing: Overnight
• Calculation:
  • Weather Severity: 0.5 (heavy snow) + 0.3 (very cold) + 0.2 (strong wind) = 1.0
  • District Factor: 0.8 (often closes)
  • Day Factor: 0.7 (Friday)
  • Timing Factor: 0.8 (overnight)
  • Probability = (1.0 × 0.5) + (0.8 × 0.3) + (0.7 × 0.1) + (0.8 × 0.1) = 0.5 + 0.24 + 0.07 + 0.08 = 89%
  • Result: High chance of a snow day

Example 3: Borderline Conditions in an Average District

• Weather data: 3.5 inches of snow, 26°F, 15 mph winds
• District: Sometimes closes (average)
• Day: Monday
• Storm timing: Overnight
• Calculation:
  • Weather Severity: 0.3 (light snow) + 0.2 (cold) + 0.1 (moderate wind) = 0.6
  • District Factor: 0.5 (sometimes closes)
  • Day Factor: 0.7 (Monday)
  • Timing Factor: 0.8 (overnight)
  • Probability = (0.6 × 0.5) + (0.5 × 0.3) + (0.7 × 0.1) + (0.8 × 0.1) = 0.3 + 0.15 + 0.07 + 0.08 = 60%
  • Result: Moderate chance of a snow day

References

• National Weather Service. “Winter Weather Safety.” https://www.weather.gov/safety/winter
• American Meteorological Society. “School Closure Decision-Making Framework for Winter Weather Events.” https://www.ametsoc.org/index.cfm/ams/policy/studies-analysis/school-closures/
• U.S. Department of Education. “Guidelines for School Emergency Operations During Severe Weather.” https://www.ed.gov/school-safety/emergency-planning