A prolonged period of excessively hot weather, typically accompanied by high humidity, that persists for several days or longer and significantly exceeds a region's normal temperature range for the season. Heat waves are among the deadliest weather hazards, disproportionately affecting the elderly, the very young and those without access to cooling. The 2003 European heat wave is estimated to have caused tens of thousands of excess deaths across the continent.
Facts
PeriodicityCommon in summer in both hemispheres, forming when a high-pressure area at roughly 3,000 to 7,600 meters (9,800 to 24,900 feet) altitude strengthens and sits over a region for several days to several weeks. 1 ScaleCommonly measured with the Heat Wave Duration Index, also used by the World Meteorological Organization: a heat wave occurs when the daily maximum temperature on more than five consecutive days exceeds the average maximum temperature by 5 degrees Celsius (9 degrees Fahrenheit), against a 1961-1990 reference period. 1 Open Questions
First DescribedNo single first scientific description found in the source consulted.
No source found naming who first scientifically described heat waves; the Wikipedia article gives modern regulatory definitions (IPCC, WMO Heat Wave Duration Index against a 1961-1990 baseline) but no historical first description, checked this pass. Identification
Distinguishing AppearanceHas no single visible form of its own; it is marked instead by its physical effects, such as roads and highways buckling and melting, water lines bursting, and power transformers detonating and starting fires. 1 Connections
Associated With
Heat waves and drought commonly reinforce one another: sustained high temperatures increase evaporation and deplete soil moisture, intensifying and prolonging drought conditions already underway.
Extreme heat during a heat wave rapidly dries fuels and increases fire behavior intensity, a documented direct contributor to wildfire risk and severity.
Demonstrated By
Desert, Biomes Source National Oceanic and Atmospheric Administration
Sources
1. Heat Wave (Wikipedia)
WikipediaCauses section (seasonal sentence)
Heat waves form when a high pressure area at an altitude of 3,000-7,600 metres (9,800-24,900 feet) strengthens and remains over a region for several days and up to several weeks. This is common in summer in both the Northern and Southern Hemispheres.
Definitions section (duration-index sentence)
A definition based on the Heat Wave Duration Index is that a heat wave occurs when the daily maximum temperature of more than five consecutive days exceeds the average maximum temperature by 5 °C (9 °F), the normal period being 1961-1990. The same definition is used by the WMO.
Infrastructure section
Heat waves cause roads and highways to buckle and melt, water lines to burst, and power transformers to detonate, causing fires.
View the Source National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric AdministrationDemonstrated By: DesertView the Source Reader Challenges (0)
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