How to Analyze Weather Conditions in Mount Aconcagua


Climbing Mount Aconcagua is full of potential risks and challenges. The fluctuating weather condition is one of the commonest challenges faced by the mountaineers on Mount Aconcagua. Adverse conditions generally last for three days after which there is stable weather for a longer duration of time. However, January and February are the best months to climb the high-altitude mountain. At the high camps, you’ll rarely find rainfall, however, you may experience precipitation in the form of snow along with some whiteouts and blizzards. Generally, the weather conditions at the high camps are very cold with temperatures at 0⁰ Fahrenheit when climbing early morning before sunrise. Furthermore, the wind chill makes the weather bone-chilling and frostbite emerge as a potential danger. However, a clear windless day on Mount Aconcagua is a good sign of great trek experience. You may even enjoy sunbath at the base camps. At Mount Aconcagua, you’ll experience a wide range of diurnal temperatures. This results in strenuous trekking and potential windburn and sunburn to the mountaineers. Therefore, covering your face and protecting your body is important with these adverse weather conditions at Aconcagua.

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Generally, dreadful storms and weather conditions are the consequences of “vaguadas”, low-pressure systems that move eastward from the giant Pacific Ocean. These storm occurrences are usually predicted by a warm front that comes before a cold storm. Furthermore, the Andes mountain ranges bring a Fohn effect, commonly known as Zonda or the viente blanco). This effect is caused due to two different climatic conditions present in the western marine and an eastern continental climate which are separated by the Andes.

Major factors that contribute to bad weather conditions

  • If you experience a low-pressure system, commonly known as “vaguadas”, moving eastward from the Pacific Ocean, it’s a clear indication of bad weather.
  • If it is raining in Santiago, you should be prepared for the bad weather.
  • If you notice local fluctuations in the barometric pressure and cloudiness on the mountain, it’s probably not a good sign.

Be alert of the following occurrences

  • If a warm front occurs, be prepared for cold front later
  • If cold front arrives from the ocean, there is higher chances of a storm on the mountain
  • Alterations in barometric pressure, cloudiness, the intensity of wind and wind directions indicate a change of weather conditions. So, be careful if you’re starting off your trek for 4 days or more.

High-altitude mountains generate their own climatic conditions which are beyond predictions. Generally, cumuli is formed at a fairly low altitude which leads to cloudy weather conditions when watched from Plaza de Mulas down the Horcones valley). These clouds are visible between 2 and 4 pm. This results in complete cloudiness in the evening and sometimes it gets cleared after sunset. These clouds appear earlier each day and when they appear between 10 am and 12 pm, it is a clear sign of a bad weather condition.

Bad weather on Mount Aconcagua can also be predicted by lensed stratocumuli and hooked cirrus which indicate a Zonda phenomenon. This is probably an indication of viente blanco or white wind, which means there will be very strong wind with snow at high altitude. The formation of giant lensed stratocumuli resembles a hat or “mushroom” on the mountain which indicates the mountaineers about the bad weather.

How to Analyze Pressure?

Plaza de Mulas uses a constant value of 4260 meters, which is 13,976 feet) for adjusting the altering pressures. Generally, the pressure tends to increase slowly from early morning to midnight and reduces eventually during late night.

Decrease in the Pressure

If you notice a gradual decrease in the pressure by 1 to 2 hPa/day while a slow rise in the temperature by 1 to 2ºC/day, 2 to 4ºF/day), you’ll have to face bad weather conditions along with cloudiness.

If the pressure is reduced abruptly (3 to 4 hPa/day), and the temperature decreases abruptly (3 to 4ºC/day, 5 to 7ºF/day), more adverse weather conditions are predicted.

If there are constant fluctuations, bad weather conditions tend to persist.

Increase in the Pressure

If the pressure increases slowly and the temperature descends slowly, this is a good sign of pleasant weather with a clear sky (or with medium and isolated cumulus). If the pressure increases from a normal pressure, which is between 599 and 601 h Pa for Plaza de Mulas, you’ll experience good weather for a longer amount of time which is corresponding to the time taken by the pressure to reach its extreme value.

If the pressure increases and the temperature decreases drastically, it is a clear indication of an unstable weather condition with temporary improvement.

If it is oscillating, weather improvements will be delayed.

Stability of Pressure

If the pressure remains stable in a low value (below 599 hPa in Plaza de Mulas), this indicates an unstable good weather. On the other hand, if both pressure and temperature are stable in an average or high value (600 hPa or more in Plaza de Mulas), this means the weather will remain unchanged.


Forecasting and analyzing changing weather patterns is an essential part of Mount Aconcagua climbing. Before you go on the trek, understand the weather trends and what will be the conditions during your time on the Mount Aconcagua.

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