What Is The U.S. Drought Monitor?

The drought monitor is the go-to product used by many meteorologists, but what exactly is the weekly map showing?

A number of factors are considered when assigning drought conditions and drought severity. Drought updates are divided into short-term and long-term drought, and drought conditions are standardized for the amount of annual precipitation a region receives.

The U.S. Drought Monitor classifies drought in five categories: Abnormally dry, then Moderate, Severe, Extreme, or Exceptional drought. Abnormally dry conditions are expected to occur once every three to five years. Moderate drought has a return period of once every five to 10 years.

In the more rare drought categories, Severe drought is expected to happen once every 10 to 20 years. Extreme drought would occur once every 20 to 50 years. Exceptional drought only has an expected return period of one to two times in a 100-year period.

The drought map is updated every Thursday, and it is a joint effort by members of the National Drought Mitigation Center at the University of Nebraska-Lincoln, the National Oceanic and Atmospheric Administration, and the U.S. Department of Agriculture.

These groups look at existing drought conditions, seasonal normals, soil moisture, rainfall, snowfall, and other variables to determine any changes to the previous drought map. Any changes to an area’s drought category are typically done by one category per week, but a major precipitation event could cause drought categories to be adjusted more significantly.

In addition to being a reference for meteorologists, the U.S. Drought Monitor is utilized by the government and the agriculture industry to adjust operations, policy, and for disaster declarations.