Like most big mountains, Aconcagua generates and attracts its own weather, making it unpredictable at times. A wide range of temperatures, from freezing nights, snowy and windy conditions, and bright sunshine intensified by the high altitude, may occur on the expedition. It can get very cold in the high camps on Aconcagua, with average temperatures 0º C/32º F during the day and -25º C/-13º F at night. Climbers on our December to January trips, may find snowfields high on the mountain, while on our February trips, members will encounter less snow and more dry, rocky terrain.
The best time to climb Aconcagua is from December to early March, during the Southern Hemisphere's summer. Days of clear sunny skies are quite normal on Aconcagua, but the mountain does receive occasional storms during the climbing season due to the muggy, humid winds blowing west off the Pacific Ocean. When this air rises over the slopes of the Andes, its speed increases and it condenses to form lenticular clouds on the summit, known as white wind (viento blanco). Southern winds are usually an auspicious sign of good weather.
In Mendoza and the lower areas along the trek, the Southern hemisphere summer temperatures fluctuate between 18-33º C/65-90º F, with warm days and cool nights.