The goal of this research was to develop a mobile sensor suite to determine plant water status in almonds and walnuts. The sensor suite consisted of an infrared thermometer to measure leaf temperature and additional sensors to measure relevant ambient conditions such as light intensity, air temperature, air humidity, and wind speed. In the Summer of 2009, the system was used to study the relationship between leaf temperature, plant water status, and relevant microclimatic information in an almond and a walnut orchard. A pressure chamber was used to measure stem water potential to represent the plant water status. Empirical prediction equations for temperature difference between leaf and air (TL −Ta) as functions of stem water potential, light intensity, air vapor pressure deficit, and wind speed were developed and validated for both crops. We found that wind speed was not significant for both crops in our experiments. Air vapor pressure deficit was significant only in almonds. The R2 values for the prediction equations were 0.71 and 0.70 for almonds and walnuts, respectively. These models were able to predict (TL −Ta) for the respective validation sets quite well. The R2 value for the validation sets was 0.76 for both crops. To improve the predictability, data measured from multiple leaves on the same tree under similar lighting conditions were averaged. The R2 values improved to 0.83 and 0.84 for almonds and walnuts, respectively when these average values were used in developing prediction equations. These results demonstrate the feasibility that the sensor suite can be used to determine plant water status.