Experiments were carried out to observe the effect of fluctuating ambient temperature and humidity on the performance of layers inside the closed system. The study was performed at El-najah Poultry Farm (closed system) in the central region in Saudi Arabia. 360 one-day-old layer chicks (Hy-line W98) were distributed randomly into three locations A, B and C in the central floor of the central line (battery) of the rearing house. At the beginning location A, centre location B and at the end of the house location C. Each location consists of 6 replicates (A1–A6, B1–B6 and C1–C6). In each replicate 20 chicks were housed. Pullets were transferred to the production house in the same farm at 17th week in the similar locations mentioned above. Each location consists of 6 replicates. In each replicate 5 birds were weighed and housed. The study revealed that, birds in location B (the centre of the house), ° where the temperature ranged (14-28 C) and humidity (22-90%), exhibited better performance than the other two ° ° locations, A and C, where temperature range (18-30 C, and 20-32 C) respectively, and humidity (30-80%, and 34- 84%) respectively. Therefore it was concluded that fluctuation of temperature inside the closed poultry house will affect the performance of laying hens.