This estimate of monthly precipitation is expressed as a rate (average millimeters of accumulated precipitation per day) for easy comparison with other months. The estimate is computed from data observed by the TRMM Microwave Imager, infrared sensors flying on the international constellation of geosynchronous satellites (geo-IR), and rain gauges. The accurate, but sparse TMI estimates are used to provide spatially and temporally varying calibration for the plentiful, but imprecise geo-IR precipitation estimates. Then the gauges are used (where available) to reduce biases and sharpen the estimates. Not only does most of the Earth's precipitation fall in the Tropics, a fair amount is concentrated in a narrow band roughly paralleling the Equator, the Intertropical Convergence Zone.