Two experiments were carried out at the Central Laboratory for Agricultural Climate (CLAC), Agricultural Research Center and the Experimental Research Station attached to the Faculty of Agriculture, Ain shams Univ., Shalakan, Qalyubyia Governorate. The experiments were conducted for two summer seasons in 2015 and 2016 under unheated multi span plastic house and under open field conditions. Both experiments aimed at investigating the effect of certain weather conditions on the impact of three insecticides used for the control of the cotton whitefly, Bemisia tabaci (Gennadius) nymphs on four cucumber cultivars. The aims of the plastic house experiment and open field experiment were to investigate the impact of certain climatic conditions (Temperature (C o), Relative humidity (%) on different insecticides efficiencies used for whitefly control compared to untreated check (without any insecticide application). Lex (Dinotefuran) insecticide was the more effect on the nymphs of B.tabaci inside the plastic house or in the open field followed by Oshin (Thiamethoxam) insecticide. However Bernastar was the lowest efficiency. Concerning effect of climatic conditions, air temperature and relative humidity affected the performance of the three tested insecticides especially during the days with temperature over 35°C.