What is a cold wave? That depends.

"Cold wave" is a commonly-heard phrase this time of year, but under what conditions do meteorologists use the expression? Mary Knapp, the state climatologist for Kansas, puts it this way:

"As used by the National Weather Service, it means a rapidly falling temperature in the next 24 hours. These falling temperatures would require substantially increased protection for
agricultural, industry, commerce and social activities."

Knapp says there are two factors that mark a cold wave: the rate the temperature falls, and the low to which it falls. These obviously vary from region to region and season to season.

"What constitutes a cold wave in Minnesota would be quite different than a cold wave in Florida," said the climatologist, who oversees the Kansas Weather Data Library, based in K-State Research and Extension. "For the majority of people, it is simply a period of very cold weather and each of us can decide what is cold!"