The map above is a cumulative rainfall map for areas of the southcentral US for the time interval of June 3 through June 10, 2004. Color patterns on the map show the amount of rain which fell in those areas for this seven day period. Maps like this were once prepared by totalling rain gauge observations, plotting them on a map by hand and contouring the map. Now NASA has rainfall measuring satellites which estimate rainfall amounts over broad areas and provide data which can be used to create computer generated images such as the map shown above.
The map was produced by the Tropical Rainfall Measuring Mission - a Joint project between NASA and the Japan Aerospace Exploration Agency.