Dear Tom,
I have heard the term “drought” kicked around recently here in the Chicago area. What is your definition of a drought?
Mary Kelszwittin, Wheaton

Dear Mary,
A single definition of “drought” is not universally appropriate because climates vary greatly from one region to another. In general, a drought is extreme dryness due to lack of precipitation over periods that are extensive both in area and time. Several kinds of drought are defined.
Permanent drought is drought that occurs when the climate of a region provides insufficient precipitation. Deserts experience this kind of drought. Precipitation episodes, when they do occur, do not give adequate moisture to insure water for long periods that occur without water,

Seasonal drought is the drought that occurs when the climate normally includes a long dry period during a portion of the year. Coastal southern California is an example, with a dry summer and rainy winter.

Sporadic drought is drought that occurs due to precipitation variability. Most of the United States, including the Chicago area, experiences this kind of drought. Such areas normally receive adequate precipitation through the year, but on occasion precipitation fails for an extensive period of time and a drought situation develops.