The U.S. Drought Monitor map identifies areas of drought and labels them by drought intensity. Abnormally Dry (D0) is not considered drought but is intended to show an area that is seeing a drying trend. The first drought category, or Moderate Drought (D1) is the least intense level while Exceptional Drought (D4) the most extreme. Drought is defined as a moisture deficit that has impacts to the environment, businesses, or individual citizens.
For more information on the U.S. Drought Monitor, its process, and the data that are used to categorize areas in drought go to the Drought Monitor webpage: https://droughtmonitor.unl.edu/