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 continental United States, based upon observed monthly precipitation totals from the U. S. nClimDiv Version 1 dataset. 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 the selected climate division, 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.
Standardized Precipitation Index
Data:
The Standardized Precipitation Index (SPI) values shown on this page are generated
using monthly precipitation totals from U. S. nClimDiv Version 1 dataset.
Data Source:
U. S. National Climatic Data Center (U. S. nClimDiv Version 1 Dataset)
Contact help@iri.columbia.edu with any questions about or problems with this Map Room.