CDC's Tracking Network uses data from the United States Drought Monitor (USDM) and the Standardized Precipitation Evapotranspiration Index (SPEI) to quantify drought severity and extent. Both of these indicators can be used to examine local and national trends in drought over time. These trends can be used to assess associations with drought-related environmental exposures and health outcomes. For more information on these data sources, see Tracking Drought.
This indicator uses SPEI data and shows the number of months of mild or worse drought per year and the maximum number of consecutive months of mild or worse drought. Data are available for all counties in the United States.
This indicator uses the USDM data and shows the number of weeks of moderate or worse drought per year and the maximum number of consecutive weeks of moderate or worse drought. Data are available for all counties in the United States. The USDM provides a consistent big-picture look at drought conditions in the United States; it is not recommended for inferring specifics about the vulnerability of local populations to drought.