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 sensing.