Observed SPI for

a)
b)

a) Time series of Standardized Precipitation Index values for the selected location for the past 10 years.

b) Time series of Standardized Precipitation Index values for the current year (thick black line), and for the three previous years (blue: 1 calendar year ago; magenta: 2 calendar years ago; grey: 3 calendar years ago).

Red dashed lines on plot a. indicate the SPI thresholds corresponding to the percentiles associated with the D0 (30%tile) to D4 (2%tile) drought intensity categories in the U. S. Drought Monitor, and green dashed lines indicate the SPI thresholds corresponding to the W0 to W4 "wetness" categories.

U.S. - Mexico Drought Analysis Tool

This map shows values of the monthly Standardized Precipitation Index (SPI) for a user-selected accumulation period (3, 6, 9, or 12-month) over the United States and Mexico, based upon observed monthly precipitation totals from the Climate Prediction Center's (CPC) Unified global precipitation dataset (combined retrospective and real-time). The SPI maps provide an indication of short-term to longer-term wet (green, positive SPI) or dry (yellow to red, negative SPI) conditions based upon precipitation alone. The negative half of the color scale uses the same colors and thresholds of SPI corresponding to the percentiles associated with the D0 (30%tile) to D4 (2%tile) drought intensity categories used in the U. S. Drought Monitor.

Additionally, the user can click on a location on the map to generate a time series graph of the selected SPI index over the past ten years for that location, and a time series graph that overlays a plot of the SPI over the past calendar year with plots of SPI for the three previous calendar years at that location.

Click and drag on the map to zoom in. To select which administrative boundaries to display on the map (including U.S. counties), mouse over the map and select the "Layers" icon. Then use the check boxes that appear to select the corresponding administrative boundaries.

Dataset Documentation

Standardized Precipitation Index
Data: The Standardized Precipitation Index (SPI) values shown on this page are generated using monthly precipitation totals at 0.5° lat/lon resolution calculated from a dataset that combines the retrospective and real-time CPC-Unified daily precipitation datasets over the U.S. and Mexico.
Data Source: U. S. Climate Prediction Center (U. S. Climate Prediction Center Unified Global Precipitation Analysis over Land, Gauge-Based Only)

Instructions

Helpdesk

Contact help@iri.columbia.edu with any questions about or problems with this Map Room.