To meet the challenge of mismatches between power supply and demand, modern buildings must schedule flexible energy loads in order to improve the efficiency of power grids. Furthermore, it is essential to understand the effectiveness of flexibility management strategies under different climate conditions and extreme weather events. Using both typical and extreme weather data from cities in five major climate zones of China, this study investigates the energy flexibility potential of an office building under three short-term HVAC management strategies in the context of different climates. The results show that the peak load flexibility and overall energy performance of the three short-term strategies were affected by the surrounding climate conditions. The peak load reduction rate of the pre-cooling and zone temperature reset strategies declined linearly as outdoor temperature increased. Under extreme climate conditions, the daily peak-load time was found to be over two hours earlier than under typical conditions, and the intensive solar radiation found in the extreme conditions can weaken the correlation between peak load reduction and outdoor temperature, risking the ability of a building’s HVAC system to maintain a comfortable indoor environment.