climate's change is one of the most important threats facing the world. That is because it causes a high ambient temperature. (UNEP, 2010). According to the report of the World Meteorological Organization (WMO, 2015), the period 2011- 2015 recorded the highest temperatures and was affected by Climate's change. Agriculture sector is strongly influenced by climatic conditions. A majority of works in agriculture are still performed outdoors under several weather conditions. High temperature, intensive insolation and elevated air humidity providing a dangerous work conditions. These weather conditions can lead to overheating (heat stress) and dehydration of the agricultural field workers. An index assessing heat stress in human beings, namely: Wet Bulb Globe Temperature (WBGT) was used in this study. This study presents the effect of heat stress from the point of view of agricultural field worker occupational health safety. Comparison of the three agricultural working conditions reveals significantly more severe heat stress in wheat threshing, rice transplanting and cotton harvesting, in terms of both the frequency of heat-stress episodes and the number of hours associated with heat stress. The WBGT maximum values during the time from 11 am up to 4 pm for wheat threshing, rice transplanting and cotton harvesting operations were 34.2 oC at 2 pm, 31.6 oC at 1 pm and 30.8 oC at 1:30 pm respectively. While the WBGT minimum values were 31.7 oC at 4 pm, 28.4 oC at 11 am, and 28.5 oC at 4 pmrespectively. The three presented work conditions are affirmed that a dangerous situation for agriculture field workers is stand. The values of the environmental parameters and its relation with heat stress during the day work hours under the previous field operations cleared that the heat stress has direct proportion with humidex and reversible proportion with air velocity and relative humidity. The agriculture field workers have exposure to hazard levels of heat stress resulting in high levels of body temperature. It is recommended to establish a sunshade for wheat thresher to provide a shade working area