The 1-month Standardized Precipitation Index (SPI-1) is a meteorological drought indicator to monitor precipitation anomalies over 1-month accumulation periods and is a proxy indicator for immediate impacts of droughts such as reduced soil moisture, snowpack, ...

The 9-month Standardized Precipitation Index (SPI-9) is a meteorological drought indicator to monitor precipitation anomalies over 9-month accumulation periods and is a proxy indicator for medium-term impacts, for example reduced stream flow and reservoir stor...

The 12-month Standardized Precipitation Index (SPI-12) is a meteorological drought indicator to monitor precipitation anomalies over 12-month accumulation periods and is a proxy indicator for medium-term impacts, for example reduced stream flow and reservoir s...

The 24-month Standardized Precipitation Index (SPI-24) is a meteorological drought indicator to monitor precipitation anomalies over 24-month accumulation periods and is a proxy indicator for long-term impacts, for example, reduced reservoir and groundwater re...

The 48-month Standardized Precipitation Index (SPI-48) is a meteorological drought indicator to monitor precipitation anomalies over 48-month accumulation periods and is a proxy indicator for long-term impacts, for example, reduced reservoir and groundwater re...