How a Snow Day Calculator Estimates the Probability of a School Closure

When snow is in the forecast, most people ask the same question: Will school be canceled tomorrow? A weather app can tell you how much snow is expected. It can tell you the temperature, wind speed, and probability of precipitation. But it doesn't usually turn all of those variables into one practical question: How likely is a school closure? That's the problem I wanted to solve with a snow day calculator. Instead of using a single snowfall threshold, the calculator combines several weather hazards and adjusts them according to regional tolerances. The result is a probability estimate rather than a simple yes/no answer. The basic idea School closures aren't caused by snow alone. A storm producing six inches of snow in a northern state can be manageable, while the same six inches in an area that rarely sees snow can cause major transportation problems. Ice, extreme cold, wind, and the timing of precipitation can change the situation considerably. The calculator therefore looks at four primary weather hazards: Snow accumulation Freezing ice and sleet Extreme cold Wind and snow drifts These are combined with the probability that meaningful precipitation is actually occurring. The core model is: P(Closure) = [1 - (1 - P_snow) * (1 - P_ice) * (1 - P_cold) * (1 - P_wind)] * P_precip The idea behind the equation is fairly straightforward. Each weather hazard contributes its own probability. The model combines those hazards into an overall risk and then accounts for the probability of precipitation. The output is capped at 99% because weather forecasting and school closure decisions are never certain. Why use multiple weather factors? Imagine two forecasts. Forecast A Snow: 6 inches Ice: 0 Temperature: 25°F Wind: 10 mph Forecast B Snow: 3 inches Ice: 0.20 inches Temperature: 15°F Wind: 30 mph Looking only at snowfall, Forecast A appears worse. But Forecast B has several additional transportation hazards. Ice can make roads slippery, extreme cold creates exposure concerns, an