An airplane‐mounted thermal scanner was used to measure irradiance in the 8‐ to 14‐μm wavelength interval over an extensively instrumented agricultural area. The area included soils differing in water and tillage condition, and replicated cotton (Gossypium hirsutum L.) plots with a wide range of plant water stress. The scanner data were recorded on analog magnetic tape and on 70‐mm film. The film densities of the various soil and cotton treatments and film calibration information were determined with a microdensitometer. The observed irradiances corresponded to cotton plant canopy temperature differences up to 6 C between the most and the least water‐stressed plots. The irradiance data from soils showed large differences as a function of time after tillage and irrigation. It is concluded that thermal imagery offers potential as a useful aid for delineating waterstressed and nonstressed fields, evaluating uniformity of irrigation, and evaluating surface soil water conditions.