Freeze–thaw cycles play a crucial impact on the degradation of outdoor structures in the northern climate regions. Outdoor structures such as bridges are located in harsh environmental conditions and are subject to daily fatigue stress, corrosion, and component rapid deterioration. Bonding carbon fiber reinforced polymer (CFRP) to the bridge element surface has proven to be an appealing technique of bridge reinforcement. This research aims to investigate and evaluate the use of externally bonded CFRP in bridge retrofits under freeze–thaw conditions. The mechanical properties of FRP systems degrade under exposure to certain environments, such as salt water, chemicals, ultraviolet light, high temperatures, high humidity, and freezing and thawing cycles. Numerical research using the finite element method is performed to examine the flexural behavior of CFRP-strengthened beams under static loading, considering the effect of freeze–thaw effect. Different freeze–thaw cycles (100, 200, 300 Cycles) are considered in finite element analysis. The results indicate that the freeze–thaw cycles under 200 cycles have a slight effect on the mode of failure of the strengthened RC deep beam, by increasing the number of cycles, the failure mode changes from tension to compression failure due to the decrease in the compressive strength of concrete.