Considerable work has been done on estimating daily fluxes at the regional scale from thermal data acquired in the early afternoon using semi-empirical models. But these studies have dealt only with clear days and homogeneous surfaces. We evaluate the use of some of these models under variable climatic conditions. A campaign of micrometeorological measurements performed from May to October 1993 on a small agricultural catchment in Brittany (NW France) allowed us to monitor the water budget and fluxes of three characteristical surfaces (meadow, wheat and stubble field). Thermal images covering the whole catchment were acquired on 7 August 1993 using an infrared camera aboard a small aircraft. They were corrected for atmospheric effects with the LOWTRAN 7 model. After geometrical corrections to superimpose these images on a digitilized land use map, a mapping of surface fluxes at the catchment scale is proposed and discussed.