The Palmer drought index, sometimes called the Palmer drought severity index (PDSI), or the Palmer Z index or simply the Palmer index, is a regional drought index commonly used for monitoring drought events and studying areal extent and severity of drought episodes. The index uses precipitation and temperature data to study moisture supply and demand using a simple water balance model. It was developed by meteorologist Wayne Palmer, who first published his method in the 1965 paper Meteorological Drought for the Office of Climatology of the U.S. Weather Bureau.