The Standardized Precipitation Index (SPI) is one of seven indices used by the Massachusetts Drought Management Task Force to determine the level of drought severity. The SPI reflects soil moisture and precipitation conditions. SPI values are calculated monthly using data in the precipitation database. These values reflect “look-back” periods of one month, three months, six months, and twelve months. The SPI values for these time periods are equivalent to the number of standard deviations from normal for precipitation totals for that time period. 

Massachusetts SPI Values for September 2016


3-Month SPI

6-Month SPI

12-Month SPI

Western Region




Connecticut River Region




Central Region




Northeast Region




Southeast Region




Cape & Islands




Drought advisory level for this indicator
The SPI is one of seven indicators considered by the Massachusetts Drought Management Task Force. See the current drought status map  to check the status of drought declarations by the Drought Management Task Force.