Standardized Precipitation Index

Overview

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The Standardized Precipitation Index (SPI), developed by T.B. McKee, N.J. Doesken, and J. Kleist and in 1993, is based only on precipitation. One unique feature is that the SPI can be used to monitor conditions on a variety of time scales. This temporal flexibility allows the SPI to be useful in both short-term agricultural and long-term hydrological applications.

View climate division based 1-, 2-, 3-, 6-, 9-, 12-, and 24-month, SPI maps going back to 1896. The data used to produce these maps are available from the National Centers for Environmental Information.

Archived Maps

Calculating the SPI

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