This study investigates the impact of cold climate weather patterns on the thermal performance of two novel designs of extruded photovoltaic thermal (PVT) collectors optimized for integration with low-temperature heat pumps. The study aims to provide a comprehensive understanding of how different weather conditions, including condensation, rainfall, frost formation, and snow, affect the thermal output of these systems. The study compares two PVT designs, one with fins attached to the thermal collector and another without, to determine the optimal configuration for maximizing efficiency under varying cold climate conditions. The results indicate significant differences in performance between the finned and non-finned designs, with the finned design showing up to 11% better thermal performance. A strong impact on the thermal performance of the PVT as a result of the different weather patterns was also observed, with up to 60% thermal gains from rainfall, and 21% thermal losses during defrosting. This research fills a critical gap in the understanding of PVT performance in cold climates and provides valuable insights that can be used to determine the appropriate control strategies for heat pumps to enhance system efficiency. The findings offer a valuable contribution to the development of more efficient renewable energy systems in regions with harsh winter conditions.