THE IMPACT of heat stress on tomato plant (Lycopersicon ……esculentum MILL.) during the late summer season was studied in the International Protected Cultivation Centre, Kafrelsheikh University, Egypt. The plants were grown in the open field and in a shaded house covered by white net providing 35% shading. The shaded house was divided into three groups, two of them grown under two fogging systems and the third one was isolated without fogging. The fogging system was operated to work 10 min/h or 20 min/h. According to the climatic data, the fogging system was adjusted to only work during the peak temperature period of the day (10 am - 4 pm). The maximum temperature was recorded at 2 pm in the open field which exceeded 37oC during the peak flowering and fruit set period. While the temperature was extremely high in the open field, the RH% was extremely low which reached to 39% at 2 pm. The results indicated that the average monthly of maximum temperature reduced 1.8 oC by shading and 4.5 oC by fogging under shading. Inside the shaded house, the RH% increased by 10% and the fogging added more 16% during the period of 10 am - 4 pm. All studied treatments mitigated heat stress on tomato plant and decreased fruit physiological disorders. Improving the microclimate inside the shaded house by fogging systems resulted in higher fruit set percentage, fruit weight and total and marketable yields than those obtained from the open field. The main fruit disorders were cracking, sunscald, blossom end rot, puffiness, internal white tissues, blotchy ripening and cat face, respectively. The most effective treatment was the use of fogging system for 20 min/h (10 am - 4 pm) under shaded house for high fruit yield and less physiological disorders during the late summer season.