A snow day is a day when schools, workplaces, or public institutions are closed because of heavy snowfall. The conditions make travel unsafe or activities impossible to carry out as normal.
The term "snow day" usually refers to an unexpected closure, especially for students, giving them a break from classes due to severe winter weather.
“It’s a snow day, so classes are canceled.”
In some areas, snow days are built into the school calendar to account for potential weather interruptions. If few snow days are used, the extra days may be taken off later in the year.
Author’s summary: A snow day means schools or institutions close because of heavy snow that disrupts regular schedules and transportation.