The objective of this study was to identify the effect of climate change within last 30 years on reference crop evapotranspiration (ETo) and to predict its future trend in the Northern coastal areas of Egypt. Correct estimating of ETo is important to determine the exact quantity of irrigated water needed for specific crop. The overuse of water for irrigation has resulted in eliminating the water resources in the whole country. Estimating ETo, which is the main input for water balance simulations, using Hargreaves, Penman Monteith, FAO Penman Monteith, Penman (Modified) and Penman Open Water models was through DAILYET version 3.0 model. The determination of ETo using simulation models, for irrigation purposes will be used as a vital tool for supporting the decision-making process in the future management of water resources and on the other hand will have a positive effect on the rest of limited water resources of Egypt. It was observed the over last 30 years, air temperature has risen by 2 degree Celsius in the study area. However, this change in air temperature did not affect the ETo estimates by using different models. Among the different methods tested, Pan Evaporation Rate method behaved the best and appeared as a simple method for accurate ETo daily estimations.