Dry spells can harm wheat and barley production, especially in dry climates. In this study, a farming index called ARID was used to model wheat and barley yields in Golestan province. By analyzing weather data and crop performance, the ARID index was found to be more accurate when using a two-layer soil-water balance model. Barley yields were more accurately predicted than wheat yields. The most sensitive growth stage to water stress varied by location, with the stem elongation stage being most sensitive for both crops in most areas. The importance of different growth stages in responding to water stress also varied by crop and location.