Saline agriculture offers promising opportunities for the production of halophytic forage crops under arid and semi-arid climatic conditions. The Mediterranean saltbush (Atriplex halimus L.), a halophytic forage plant that can withstand a variety of harsh climatic conditions, is affected by seasonal climate changes in terms of growth and productivity. The objective of the current study is to comprehend how climatic changes affect the Mediterranean saltbush’s growth and productivity in semi-arid environments. Plant samples were collected every 3 months from the Mediterranean saltbush cultivated on saline sandy loam soil (15 dS m⁻¹). Biomass yields, nutritional value, and biochemical components were recorded. The studied plant produced 8.55 Mg ha⁻¹ of dried stems and leaves yearly, with the leaves contributing 31% of the plant’s overall dry yield. The dried stems and leaves yield of the Mediterranean saltbush declined by 50 and 45% in the summer season compared to the spring. The summer leaves of the Mediterranean saltbush had higher concentrations of Na, K, and Cl than the winter leaves. In contrast to chlorophyll concentrations, which increased in the spring and decreased throughout the other growing seasons, proline concentrations in the leaf tissues changed throughout the year in the opposite direction. The Mediterranean saltbush reduced the chlorophyll and relative water content in the summer months and increased the leaf Na, K, Cl, and proline. The Mediterranean saltbush plants regulate the proline levels as well as some ions like Na, K, and Cl to achieve an osmotic adjustment in the leaf’s tissues. The Mediterranean saltbush plants can produce fodder that is high in protein, nutrients, and nutritional value under conditions of extremely salty soil and irrigation water. These results provide a good opportunity to exploit water and saline lands in the production of animal feed, which helps in implementing sustainable development plans in semi-arid regions.