The availability of digital cameras for use in airborne image acquisition supports site specific irrigation management as it satisfies spatial, spectral and temporal requirements for precision agriculture. Traditionally, surface temperature can be derived by regression analysis of the known temperatures on the ground and thermal digital counts. The absence of ground control temperature measurements has been a challenge. This paper describes a method in estimating and standardizing surface temperature useful in crop water stress assessment. The technique is based on weather station data, soil brightness and ground cover information.