It is important to know that the Aconcagua Park is located in a very rigorous and variable climate zone, emphasizing that it is within the central Andes characterized by cold climates, with strong winds and with the low humidity, which comes from the anticyclonic centers of the Pacific Ocean. This causes low amounts of oxygen.
How does this type of climate work? The winds from the east rise and collide with the mountainous mass of the range, cooling and precipitating their moisture with snow on the high peaks. Subsequently, the masses of air already have dried, descend on the eastern flanks of the mountain range warming progressively. The same is the cause of snow storms and strong winds that are unleashed on Aconcagua as well as thunderstorms.
This mountain, due to its large size, is also a particular phenomenon where strong winds blow from the west, at high altitudes, affecting the upper part of the mountain (5,500 meters above) forming a large "mushroom". This is a very attractive landscape but a sign of a terrible forecast for mountaineers. This ¨mushroom¨ is a symbol of "pesto," bad climate where "the mummy is coming" being said in the mountains, meaning strong winds and precipitations. When the "mushroom" appears, it is not advised to stay in the upper part of the mountain as it could be fatal.
As for the temperatures recorded during the summer, it is necessary to consider that during the nights (even in good weather), about 5,000 m.a.s.l, the temperature is about -20 ° and at the top, it is frequent to register -30°C. During periods of bad weather or in the presence of air masses coming from the South, in Plaza de Mulas (base camp) it is already frequent to register -18 ° C, whereas in the upper part of the mountain -25°C are not uncommon.
In winter, the Aconcagua is rarely visited. Its temperature never rises to 0 ° C, besides being lashed by strong winds and constant snowstorms. Extremely low temperatures are recorded in shady places on the mountain. An ascent to the Aconcagua in winter would be a very important psychophysical test and for that, a good team is needed, besides a lot of confidence, experience and a special permit, which is very difficult to obtain.