NOAA Drought Indices

Historical Palmer Drought Indices

Georgia Division 9 Monthly (1895-present) - Historical drought index data sets and plots for Georgia coastal counties

All Climate Divisions Monthly (1895-present) - Data for all US climate divisions can be browsed and downloaded (formats)

Map of climate divisions (NOAA)


Palmer Drought Severity Index: attempts to measure the duration and intensity of the long-term drought-inducing circulation patterns. Long-term drought is cumulative, so the intensity of drought during the current month is dependent on the current weather patterns plus the cumulative patterns of previous months. Since weather patterns can change almost literally overnight from a long-term drought pattern to a long-term wet pattern, the PDSI can respond fairly rapidly.

Palmer Modified Drought Index: Operational version of the PDSI. Description available in Heddinghaus and Sabol (1991).

Palmer Hydrological Drought Index: measures hydrological impacts of drought (e.g., reservoir levels, groundwater levels, etc.) which take longer to develop and longer to recover from. This long-term drought index was developed to quantify these hydrological effects, and it responds more slowly to changing conditions than the PDSI.

Palmer Z Index: measures short-term drought on a monthly scale.



This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959 and OCE-1237140. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.