|Extreme weather includes unusual, severe or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. |
Often, extreme events are based on a location’s recorded weather history and defined as lying in the most unusual ten percent.
|Heat waves are periods of abnormally high temperatures and heat index. Definitions of a heatwave vary because of the variation of temperatures in different geographic locations. Excessive heat is often accompanied by high levels of humidity, but can also be catastrophically dry.|
A cold wave is distinguished by a cooling of the air. As used by the U.S. National Weather Service, a cold wave is a rapid fall in temperature within a 24-hour period requiring increased protection to agriculture, industry, commerce, and social activities. The precise criterion for a cold wave is determined by the rate at which the temperature falls, and the minimum to which it falls.
Cold wave in continental North America, Dec-03 to Dec-10, 2013