National Agroclimate Series of Derived Indicators (NASDI) - Standardized Precipitation Index (SPI)

National Agroclimate Series of Derived Indicators (NASDI) - Standardized Precipitation Index (SPI) is an open dataset from Agriculture and Agri-Food Canada with 6 files (ESRI REST, GEOTIF, PDF); catalogue record updated 2026-05-26. On CanQuery you can follow the original downloads. Files are available in English and French.

The Standardized Precipitation Index (SPI) is widely regarded as one of the most accessible tools for quantifying and reporting meteorological drought. At shorter timescales, SPI values are highly correlated with soil moisture, while at extended timescales, they reflect variations in groundwater and reservoir storage. The SPI model derives probability distributions from historical precipitation records, which are then normalized using an incomplete gamma function across multiple timescales. SPI values indicate the number of standard deviations the observed anomaly departs from the long-term period of record, with positive values corresponding to wetter-than-average conditions. Time periods calculated for monthly precipitation percentiles are 1, 2, 3, 6, 9, 12, 18, 24 months. Each ISO week is numbered from 1 to 52 (sometimes 53) within a year. An ISO week starts on Monday and ends on Sunday. Historical record goes back to 1980 Indices values were calculated using the xclim python package The National Agroclimate Series of Derived Indicators (NASDI) products provide a collection of comprehensive and regularly updated datasets on key agroclimatic variables, including accumulated…

Publisher

Agriculture and Agri-Food Canada

Resources

6

Catalogue metadata updated

2026-05-26