Standardized Precipitation Index User Guide WMO-No.1090

Over the years, there has been much discussion on what drought indices should be used in a particular climate and for what application. Many drought definitions and indices have been developed and attempts have been made to provide some guidance on this issue. We hope that this user guide on the Standardized Precipitation Index will help countries and institutions to understand how to calculate and use the SPI in order to develop or further enhance their own drought monitoring and early warning capabilities.