This study was conducted to evaluate the influence of heat stress on physiological and blood Parameters in twenty one Sohagi female ewe lambs in the experimental sheep farm of Animal Production Department, Faculty of Agriculture, El-kawthar city Sohag University, Egypt. Twenty One female ewe lambs 9-11 month of age with average body weight 25.55±2.69 Kg were divided into three groups according to daily exposed period to direct sunlight. In the first group, female ewe lambs were housed in indoor barn away from direct sunlight and considered as control group (T0), while those in the second and third groups were daily exposed to direct sunlight in outdoor barns for 4 hours (T4) and 8 hours (T8), respectively. The experiment lasted for 30 days during august in the summer season (preliminary period = 10 days + collection period = 20 days), the temperature-humidity index (THI) values for indoor and outdoor barns were 80.71 and 85.15 respectively, which indicated that experimental groups which exposed to direct sunlight were subjected to severe heat stress conditions. Results were showed that there statistically significant increasing in rectal temperature and respiration rate of Sohagi female ewe lambs in T4 and T8 than T0 (RT 39.15, 39.41 vs. 39.47 Co, RR: 67.9, 89.1 vs. 99.8 Panting/min., respectively). Also, studied blood parameters of experimental animals were affected significantly by heat stress conditions and direct sunlight. It could be concluded that sheep suffer from heat stress in arid areas, so it is recommended to keep it away from direct sunlight and high ambient temperature which are the most important factors of heat stress in tropical conditions.