Canadian highway bridges are aging and giving rise to safety concerns. Frequent monitoring and significant investments are required to maintain their safety and serviceability levels. Corrosion of steel in reinforced concrete (RC) bridges leads to deterioration of materials, reduction of load-bearing capacity and increased maintenance costs. There is concern that climate change may further accelerate and amplify existing and new deficiencies alike, increasing the rate of corrosion and imposing new extreme loads on existing infrastructure. A now common technique for rehabilitation consists of externally bonded (EB) fibre-reinforced polymers (FRP) in critical locations of RC components to improve their overall structural performance. This technique has been shown to provide increased load-bearing capacity for damaged girders, however, there remains uncertainty related to their effectiveness when subjected to high environmental temperatures, especially when combined with corrosion damage. A two-span simply supported prestressed RC highway bridge was designed based on a review of existing bridges in Canada. A parametric study was conducted on this bridge to examine the effects of EB FRP rehabilitation on its performance when subjected to various levels of flexural reinforcement corrosion. The composite effects of heatwaves on the rehabilitated bridge were also investigated to assess their influence on the load-carrying capacity and serviceability levels. The study managed to quantify the ultimate strength and serviceability levels of EB FRP-strengthened bridges. This information will help determine the rehabilitation requirements of existing infrastructure, enabling adaptation to emerging challenges posed by climate change in the upcoming decades.