In the context of the overhaul of the WMO/CIMO guide (no. 8) on instruments and methods of observation, we performed an experiment to quantify uncertainties in air temperature measurements due to reflected solar radiation from a snow-covered surface. Coupled sensors with different radiation shields were put under different ground conditions (grass vs. snow) for a whole winter. Results show that different shields may reduce the influence of backward radiation, which can produce errors up to 3 °C.