There are risks for indirect air-cooling generators running under extreme climate conditions. Without proper control, they would cause operation safety problems, such ase radiator tube bundle freezing and great fluctuation in condenser vacuum. Based on the practical operation of two newly built units operating in extremely cold, hot and windy weather, this paper analyzes and studies the factors and mechanism that affect the unit secure operation in climate extremes. and a set of preventive measures are proposed to eliminate the risks. These measures can safeguard the indirect air-cooling units operating safely and reliably under extreme weather.