The purpose of this study is to determine the size of air temperature changes with altitude in the mountains of the arid zone,on the example of the Upper Dades valley (High Atlas,Morocco).The air temperature change with altitude was determined on the basis of 5 years data from three meteorological stations.The analysis was carried out on an annual and seasonal basis.The annual and daily variations of thermal gradients between pairs of stations were also determined.It was found that the average thermal gradient in the Upper Dades valley was-1.02℃ per 100 m.The highest values of the thermal gradient occur in winter and the lowest in summer.In winter,the thermal gradient was characterized by the greatest variability.Minima of the daily variation of air temperature gradients were observed in early morning hours and maxima around midday.In the lower part of the valley,air temperature inversion frequently developed between 10 AM and 3 PM UTC.The obtained results show high thermal gradients in the mountains of the arid zone,with their annual amplitude increasing in the lower parts of the valley.The instantaneous values of the gradients were significantly modified by the supply of latent heat and the occurrence of dust storms.It has been shown that the advection factor plays an important role in shaping large gradient values.The study contains novel results of thermal gradient measurements in high mountains of arid zone.