The National Weather Service describes a cold wave as a rapid drop in temperature over a 24-hour period that necessitates some type of protective action. Impacts of cold waves can apply to commercial, agricultural and social activities.
Alternative criteria for a cold wave are used by some organizations. The Weather Channel states that a cold wave requires at least two days where temperatures are below normal in at least 15 states. Furthermore, temperatures must be at least 15 degrees colder than climatology normals in at least five of the affected states.
Cold waves may affect areas that typically enjoy moderate winters such as the state of Texas. In one example of a cold wave, temperatures near Dallas, Texas dropped to 8 degrees Fahrenheit in February of 1996, in the midst of a five day block of excessively cold conditions.