Target Date Lead Time Issue Date




IRI Seasonal Precipitation Forecast

This map shows seasonal precipitation forecasts from the International Research Institute for Climate and Society. In areas of Africa where the presence of water allows for mosquito vector development, skillful seasonal precipitation forecasts may provide early warning of risk of an epidemic.

Seasonal Precipitation Forecast Legend

Research has shown that sea surface temperatures in the Indian Ocean influence temperature and precipitation patterns in Africa.

One of the main advantages of using sea surface temperatures in the Indian Ocean to predict precipitation in Africa is the "teleconnection" effect.

Using teleconnections, or lagged effects of sea surface temperatures on precipitation elsewhere, we can make forecasts with 1-6 month lead times.

This map uses that relationship to produce precipitation forecasts for specific seasons.


Barnston, A., Mason, S., Goddard, L., DeWitt, D., Zebiak, S.(2003). Multimodel Ensembling in Seasonal Climate Forecasting at IRI. Amer. Met. Soc. 84 (12): 1783-1796.

Goddard, L., Graham, NE.(1999). Importance of the Indian Ocean for simulating rainfall anomalies over eastern and southern Africa. J. Geo. Res., 104, 19099-19116.

Dataset Documentation

IRI Seasonal Precipitation Forecasts are produced monthly on a 1.0 degree spatial resolution basis.

Precipitation Forecasts

Monthly Total Precipitation Forecast on a 1.0 x 1.0 deg. lat/lon grid
Data Source
(Forecast Division from IRI: International Research Institute for Climate and Society)

Climatology of Precipitation

Monthly Temperature on a 2.5 x 2.5 deg. lat/lon grid
Base Period: 1 Jan 1981 to 31 Dec of last year
Data Source
(Forecast Division from IRI: International Research Institute for Climate and Society)


Access the dataset used to create this map.


Contact with any technical questions or problems with this Map Room.


The IRI Seasonal Forecast interface allows for graphs to be made easily by pointing and clicking on a location anywhere in the world.

The graph shows the probability, or chance, that the target date being forecast will fall into certain categories relative to "normal" or average conditions.

The three categories are below normal, normal and above normal.

"Normal" conditions are defined as the average temperature for the forecast month(s) at the selected location since 1980. An above (below) normal forecast indicates there is confidence that precipitation for that season will fall within the top (bottom) 33% of the observed average precipitation.

The interface also allows for the month in which the forecast was issued to change. This may be useful to determine how a forecast for a specific area at a fixed target date has changed from older forecast to newer forecast.