A detecting assembly and method for identifying and tracking clouds in a zone of the sky being observed where some thermal-infrared flux emitted by the zone is collected and transmitted to a thermal-infrared detector, the detector including a sensor sensitive to the flux in a set band of wavelengths, a measurement of the actual temperature and actual relative humidity of the air at ground level is carried out and the vertical temperature and water vapor distribution is deduced therefrom, the dataset relating to the thermal-infrared signal emitted by a reference sky for the vertical temperature and water vapor distribution is stimulated or obtained, the dataset thus simulated or obtained is subtracted from the dataset measured by the sensor to determine if clouds are present in the zone, and the dataset thus obtained is processed in order to compute the optical thickness and/or altitude of each cloud in the observation area.