Sunday, November 27


A newsletter forwareded to my email by Aymara Adventures and Expeditions a day before I leave for Argentina. I just want to have a copy of it as my reference.

Mendoza City
Our expedition programs start in Mendoza City. Since these trips take place during the summer, and since our province is in a semi desert weather region, it is very usual that during midday and in the afternoon, temperature ascends to 35ºC or 40ºC. During the night, temperature descends and you may need a coat, since it is not strange for it to be 15ºC.
Weather during the approximation to Base Camp
As we get closer to the base camps at Mt. Aconcagua, we might find a difference in temperature between day and night. With good weather conditions, on a sunny day the temperature might be very nice; approximately 25ºC. Normally, during midday the wind starts, turning the weather unstable during the afternoon. By the end of the day the wind calms down and the nights go on quietly. During the nights the temperature reduces considerably, and it is possible to experience temperatures of 0ºC or even colder. For this reason, you must be prepared for these changes and carry adequate equipment and clothing. During the trekking in this first stage of approximation, it is important to bring a coat, preferably a rainproof coat that protects you from the wind or occasional snow that might surprise us on our way. It is also necessary to put a pair of gloves in your backpack and a pair of sandals is also important to have, since in the afternoon, it is very common to cross rivers. All these cautions are necessary, because it is better to be prepared - taking into account the varying weather conditions above 3.000 m.

Weather during the ascent, up above 4.300 m

Aconcagua climbing season takes place during the summer (December, January and February). During these months the mountain generally has good and stable weather conditions, but it may change very quickly. Weather forecast is not very precise in this region.
Atmospheric pressure and the sky, are some of the signs that our guides and other people use in the mountains in order to forecast weather.
A particular detail that is very possible to observe in this part of the Andes, is the formation of a lenticular cloud, very high up, known as the "HONGO". This sits at the top of the mountain, very still. It is formed by powerful air streams coming from the west (from where most of the storms come) and it moves over 5.500 m. Being in the presence of the "Hongo" during your expedition on Mt. Aconcagua is, undoubtedly, a sign of alert to take into account when planning our ascent, even if we have good weather conditions in the valleys and base camps.
It is also very common, to be in the presence of electrical storms. As we get higher, weather conditions turn more rigorous with regards to temperature. During the day, temperature will not rise more than 0ºC and sometimes, we might be walking with -15ºC. In the higher Camps, like in Berlin or in Camp 2 at the base of the glacier, we will experience temperatures of -25ºC to -35ºC during the night. Icy and persistent wind is constant on Mt. Aconcagua, making the temperature lower than the thermal sensation; it can make you freeze in a few minutes. These low temperatures along with the strong wind can result in a terrible white wind storm. This phenomenon is produced by the wind separating us from the floor and everything turning completely white (Blizzard).

In moments such as these, goggles are essential. We will, however, feel the harshness of the wind even on a sunny day and with good weather conditions, especially very early in the morning, when we have left the warmness and comfort of our tents, in search of the summit.

Weather during the summit day

Undoubtedly this section of the mountain has the hardest weather conditions. The day we start the ascent to reach the summit, we leave one of the highest camps very early. This is a very demanding experience, in which the wind can produce temperatures of -25ºC or -30ºC. Eventually, it may be harder during the first hours in the morning, than staying in the summit by midday when the sun warms us, and it is possible to have temperatures of 0ºC.
Teacher Cesar A. Mochi
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