Free Snow Day Calculator (+ Guide)

What is a snow day calculator?

A snow day calculator looks at the weather forecast for the night and morning before school, and tells you how likely a closing is.

This one shows you the forecast it's reading. The signals are your school's usual lines and the alerts the National Weather Service has out.

How it works

Pick your town and the calculator asks the National Weather Service's API for its forecast. Nothing else about you leaves your browser.

What it reads from the forecast

For each morning it reads the NWS grid forecast for your town, in your town's own time zone.

It also shows the chance of rain or snow, the temperature at 7 am and the snow every 6 hours for 3 days.

Why there's no percentage

Districts close for different amounts, and weather that shuts one school may not shut another.

The NWS works the same way: each office issues warnings on local criteria, so the snow for a Winter Storm Warning is typically much higher in the Northern Plains.

So instead of a made-up number, you set your school's lines. If you don't know them, last winter's closings are a good guide.

Winter alerts, explained

The National Weather Service uses three levels, and the calculator lists any that are in effect for your town.

An Ice Storm Warning is usually issued for about 1/4 inch of ice or more, and a Blizzard Warning for gusts of 35 mph or more with snow cutting visibility.

Wind chill and the trip to school

Wind chill is how cold it feels on skin. The NWS wind chill chart gives an example: at 0°F with a 15 mph wind, it's -19°F, and exposed skin can freeze in 30 minutes.

Frostbite needs air below freezing, the NWS adds. Districts can close or delay for extreme cold too, so the calculator lets you set that line.

Mistakes to avoid

These are the slips that come up most.

• Reading tonight's total as snow on the ground by morning, when some falls after school starts
• Ignoring ice, which can close roads with no snow at all
• Checking once the evening before, when the forecast can change overnight
• Using another district's lines for your school

Who is the snow day calculator for?

It's for students, parents and teachers watching the forecast on a school night, and these tools help around it.

• Sleep calculator – for a bedtime that ends a sleep cycle
• Electricity cost calculator – for what a space heater costs to run
• Gas trip calculator – for the fuel on a winter drive
• Christmas countdown – for the days until the winter break's big day

Check again in the morning, since the forecast can change overnight.