A weather cancellation or delay refers to the closure or postponement of schools, businesses, or events due to severe conditions such as snow, extreme heat, flooding, or cyclones. The central factor is safety, particularly the risk to school buses and pedestrians, though the threshold varies by region—communities used to harsh weather often remain open. In North America, these closures are famously known as "snow days", where classes are cancelled even if the building technically stays open, and schools typically build extra days into their calendars to accommodate them. If those built-in days run out, schools must make up the time later in the year, although state departments (like Texas in 2015) can issue waivers to skip the make-up days. Increasingly, institutions are also closing for "heat days" due to extreme temperatures, with districts like San Diego Unified adopting specific operational procedures for rising heat.