A technique for estimating water contents within the root zones of crops from measurements of midday leaf‐air temperature differentials is developed. Pertinent data used in the analysis were obtained from a cotton crop and two sorghum crops grown on an Avondale loam at Phoenix, Arizona. Since air temperature is the most commonly measured meteorological parameter on earth, and since crop canopy temperatures can be obtained by radiometric means, the technique appears to point the way toward the eventual development of a procedure for the estimation of crop yields via remote sensin