Downloaded from https://www.everyspec.com world. During summer in these areas, temperatures above 110 ° F (43 ° C) occur frequently, but except for a few specific localities, temperatures will seldom be above 120 ° F (49 ° C). In winter, temperatures are not likely to be extremely low so that the low temperatures of the basic climatic design type apply. If materiel is designed only for the hot type, a special recommendation for low temperature design values should be sought. Limited portions of this area are sometimes subject to very high absolute humilities, although the highest temperatures and highest dewpoints do not occur at the same time. b. Basic climatic design type.
The area this type applies to includes the most densely populated and heavily industrialized parts of the world as well as the humid tropics. The entire range of basic design conditions does not necessarily apply to any one place. Each single design condition (high temperature, low temperature, high humidity) applies to a widespread area. When taken together, the design values should provide for satisfactory equipment throughout the area involved. Tropical areas are included in the basic climatic design type because the temperature of the humid tropics is quite moderate, and the humidity is also experienced in the midlatitudes.
The unique feature of the tropics that makes it important to materiel is the persistence of high humidity over long periods of time. This condition not only promotes corrosion but is an excellent environment for insect and microbiological damage. c. Cold and severe cold design types. The areas designated as cold, and severe cold, primarily northern North America, Greenland, northern Asia, and the Tibetan Highlands of China, were delimited because of the occurrence of low temperatures. In the area of the cold design type, temperature during the coldest month in a normal year may be colder than the basic cold extreme of −25 ° F (−32 ° C).
In the severe cold areas, temperature during the coldest month in a normal year may be colder than the cold extreme of −50 ° F (−46 ° C), but colder than −60 ° F (−51 ° C) no more than 20 percent of the hours in the coldest month in the coldest part of the area (northern Siberia where absolute minimum temperatures as low as −90 ° F (−68 ° C) have been recorded). Because the extreme low temperatures are not controlled by a daily solar cycle, they persist for a long enough period of time for materiel to reach equilibrium at a temperature near the minimum. d. Absolute maximum and minimum temperatures.
Figures 2-2 and 2-3 are included to show the absolute maximum and minimum temperatures that have been observed. The maps are generalized because of data limitations and the uneven occurrence of extremes. (Fig. 2-2 and 2-3 were originally fold-ins at the end of the regulation. In this electronic version, they have been reduced here and are presented in context.) 22 AR 70–38 • 15 September 1979