The humid airflow blowing West from the Pacific, collides against the mountain range and moves up its slopes cooling its temperature and turning its humidity into snow. When these winds reach the other side of the mountain, it has become dry and warm.
During the summer season thunderstorms are violent, being the strokes of lightning a potential danger, specially, in the summit, crests, and the North-West side.
Occasionally, there are strong drafts blowing from the West which are stronger in the highest portion of the peak, above 5000m over sea level. Sometimes in Plaza de Mulas the weather seems to be good, but there is an atmospheric phenomenon that indicates the opposite in higher altitude; that is a mushroom shaped cloud which is a clear sign of storm, making the climbing impossible.
The summer season is extremely cold, around 5000m the temperatures at night are -20ºC and above 6500m they are -31ºC. When the wind blows from the South or in stormy conditions the temperature cools to -20ºC at the base camps and -27ºC in the summit.
The thermal amplitude during day and night allows you to wear light clothing in the base camps and even in the summit.
Winter in Aconcagua is harsh being -0ºC the media temperature.
