What is a cold day?
A cold day is a school closure caused by dangerously low temperatures or wind chill rather than by snow or ice. Cold days are most common in the northern United States, the Great Lakes and Midwest, the northern Plains and across much of Canada, but a polar vortex or arctic blast can bring them to places that rarely see them.
The reasoning is simple. Children waiting at a bus stop, walking to school or standing outside for pickup are exposed to the cold for long stretches, and the risk rises quickly as the wind chill falls.
Air temperature versus wind chill
Air temperature is what a thermometer reads. Wind chill, or the feels-like temperature, describes how cold the air feels on exposed skin when you account for wind. A calm 0°F morning is cold. A 0°F morning with a stiff wind can feel like something far colder, and exposed skin can be harmed much faster.
That is why districts that publish a cold weather policy usually base it on wind chill rather than air temperature. If you live somewhere that gets very cold, look up your district's cutoff, since the number varies from place to place.
Other ways extreme cold disrupts school
- Bus trouble. Diesel engines can be hard to start in extreme cold, and mechanical problems rise.
- Building systems. Frozen or broken pipes and heating failures can close individual schools.
- Power demand. Cold snaps strain the electric grid and can lead to outages.
- Waiting outside. Children without proper winter clothing are especially at risk at stops or in drop-off lines.
How the calculator counts cold
The calculator looks at the lowest feels-like temperature during the morning commute window, roughly 5 to 9 AM. Points begin to build when the feels-like temperature drops below about 18°F (-8°C) and keep rising as it falls, reaching their maximum near -12°F (-25°C). When more than an inch of snow is also forecast, strong gusts add more points, since wind drives drifting and poor visibility.
Because cold is scored separately from snow, a clear but bitter morning can still produce a meaningful snow day chance, particularly with the district setting turned up for areas where cold days are common.
Blowing snow, whiteouts and drifting
Wind adds a second problem even when little new snow falls. Loose snow already on the ground can blow across open roads, forming drifts and cutting visibility to near zero. Rural districts in open farmland are especially exposed. A forecast with strong gusts, lots of loose snow and bitter cold is often a recipe for a closure, with or without fresh snowfall.
What to do on a very cold morning
- Dress children in layers, with a hat, mittens or gloves, a face covering and insulated boots.
- Limit time outdoors and let kids wait for the bus indoors or in a warm car if you can.
- Keep your car's gas tank at least half full and keep a blanket and charger inside.
- Check on neighbors, older adults and pets.
Want to see how cold your own morning looks? Use the snow day calculator.