A drought is defined as a period of abnormally dry weather, lasting long enough to produce a serious hydrologic imbalance such as a reduction in water supplies, loss of hydrologic generation capability, crop damage or other related events. Many do not realize that the effects of a drought can have serious economic impacts, even though it may not be as spectacular as a flood, tornado, or hurricane. While not as spectacular, droughts do pose a significant effect which may be ore costly than those other types of disasters. No region in North America is immune to periodic droughts, and in any given year, at least one region experiences drought conditions.

The most famous North American drought of the 20th century is the 1930s Dust Bowl drought. This drought affected the Great Plains and lasted for approximately 7 years, affecting 50,000,000 acres of land and ruining crops. A significant impact was the resulting mass migration of millions of people from the Great Plains to the western U.S., which was well documented by John Steinbeck's novel 'The Grapes of Wrath.'

Four different definitions ways that droughts are defined are:

• Meteorological - the departure of precipitation from normal. Since various regions have different normals, no standard difference has been established.
• Agricultural - a condition where the amount of soil moisture is sufficient to meet the needs of the particular crop.
• Hydrological - a condition where surface and subsurface water supplies are below normal.
• Sociological - a condition that exists when the physical water shortage begins to affect people.

North American summers are hot; most summers see heat waves in one section or another of the United States. East of the Rockies, they tend to combine both high temperatures and high humidity although some of the worst have been catastrophically dry. During heat waves, the human body is taxed beyond its abilities and deaths occur. During the heat wave of 1980, more than 1250 people died and many more were significantly affected. Heat waves in cities become oppressive, as the heat wave traps pollutants in urban areas and adds to the stresses of existing severe pollution. Areas where air becomes trapped, such as alleys and towers of inner cities, create additional conditions that contribute to deaths and other disorders, especially for those without air conditioning.

Heat related illness can be very severe on the elderly, small children, chronic invalids, overweight individuals, and those taking certain medications, drugs and even alcohol. Specific precautions should be taken, and those who feel they may be at risk should discuss their condition with a physician.