Heat Waves and Drought

Over the past 30 years, excessive summer heat has killed an average of 131 people in the U.S., which accounts for more deaths each year than from lightning, hurricanes, tornadoes, floods, or earthquakes. Combined with drought conditions that often accompany heat waves, economic losses can be in the billions of dollars.

Image source: Quayle, Robert, and Fred Doehring. “Heat Stress: A Comparison of Indices.” Weatherwise, vol. 34, no. 3, 1981, p. 121. 

Apparent Temperature

A heat wave in the Kansas City area is a prolonged period (two or more days) of intense heat and humidity where the heat index temperature is 105° or higher. In 1979, Robert Steadman developed a heat index that is the basis of indices used today. Steadman’s index uses a formula of air temperature, moisture, and other factors to determine an “apparent” temperature.

Image source: The Palmer Drought Severity Index map during the drought of 1977. “The Palmer and Crop Moisture Indices.” Weekly Weather and Crop Bulletin, vol. 62, no. 31, 1977, p. 14. 

Drought Monitor

Drought is a deficiency in precipitation over an extended period, usually a season or more, resulting in a water shortage causing adverse impacts on vegetation, animals, and/or people. Wayne Palmer, a meteorologist with the U.S. Weather Bureau, published his drought index in 1965. The Palmer Index was the main drought index in the U.S before the establishment of the U.S. Drought Monitor in 1999. Today, it is one of five indices used to compute the Drought Monitor.