We present a method for computing the daily outgoing longwave radiation flux for remote sensing purposes. The proposed algorithm only requires the NOAA Advanced Very High Resolution Radiometer (AVHRR) derived surface temperature in the early afternoon, the minimum air temperature from the meteorological network, and the day duration computed from the site coordinates and the date. The model is validated against a large experimental data set, with a resulting rms error of about 6.2 DJ.cm−2 (less than 2% of the mean radiation) at the daily scale. The possible use of the algorithm for mapping daily net radiation is finally illustrated by two examples, in the South-West of France and in Niger.