Climate change presents a significant challenge to water resource management in Egypt, particularly concerning agricultural irrigation. Egypt's principal water source is the Nile River under escalating strain from elevated temperatures, erratic precipitation, and severe weather phenomena. This study analyzes maize (Zea mays L.), an essential crop in Egypt, and its irrigation requirements over four decades (1982–2021) concerning climatic changes. The FAO-Penman-Monteith equation was utilized to compute reference evapotranspiration (ET0) and evaluate maize water needs using Cropwat program. The computation was conducted based on meteorological data for the Al-Gharbiya, Assiut, and Aswan governorates, sourced from both the Climwat program and NASA's POWER. The results indicate that ET0 increased in all regions, with Aswan exhibiting the most significant increase, rising from 7.77 mm/day between 1982 and 1991 to 8.09 mm/day from 2012 to 2021. The water requirements for maize reached their zenith during the mid-growth stages, attaining a maximum of 136 mm in Al-Gharbiya and 194 mm in Assiut from 2002 to 2011. During the study period, net irrigation for maize escalated across all governorates, with Aswan's net irrigation requirement increasing from 1,316 mm in 1982-1991 to 1,342 mm in 2012-2021. The findings verify water demand increases, especially in areas such as Aswan, where elevated temperatures intensify water loss. The research highlights the significance of effective irrigation methods and sophisticated technologies to address increasing water demands and guarantee sustainable maize cultivation in Egypt's water-scarce context. These insights are essential for formulating climate-resilient agricultural strategies and alleviating the effects of water scarcity.