Climate

Summary of information found in publications on the Aysen region, relevant to valley Leones, located east of the Andes between the lake General Carrera and the Northern ice field:


The following should be read taking into account the moderating effect of lake General Carrera: valley Leones has significantly less extreme weather than places further away from the lake, for example cities of Coyhaique and Balmaceda.


The Aysen region experiences throughout the year a strong influence of the polar front that sits above it; disturbances associated with it impart marine characteristics on the West of the Andes, which become progressively continental on their Eastern slopes. There are four major climate types: mildly cold and rainy, continental trans-andean with progressive change into steppes, cold-steppe and ice cold by height effect.


Valley Leones belongs to continental trans-andean climate with progressive change into steppes, which extends from the river Cisnes to the south end of the region:

This area differs from the others because it is protected by the mountain range of the Andes, which allows a significant decrease in rainfall compared to the sector of archipelagos on the same latitude. The climate of the eastern slope of the Andes is a gradual transition to cold steppe climate.

Roughly two parallel areas are recognized in the region, extending from north to south, with completely different climates as to their biological effects: the eastern or trans-Andean area has a more arid climate with significant annual temperature fluctuations, under strong influence of neighboring bioclimates of Argentina, especially in terms of increasing some continental trends. Aysen is no doubt a transition zone between the two areas, experiencing even faintest Mediterranean influences.


A study of seasons of the eastern part  shows a progressive increase towards the south of the "vertical integration" of temperature and humidity graphs as the Mediterranean influence is totally disappearing. The relative humidity decreases southward in the trans-andean part, falling in Chile Chico to just 50% of its initial value; in this town, in addition, the strong decrease in rainfall is associated with relatively high temperatures due to a favorable influence of Lake General Carrera (lake Buenos Aires), which forms peculiar xerothermic characteristics.


In this part of Patagonia the weather is dominated by two factors. The first, and there is no equivalent part in the world in which this factor plays such a crucial role, is the very strong and highly predominant west wind while the second one are the Andes and their ice fields.

Wind: This region has strong west winds year-round without any major positive or negative deviation, i.e. they are nearly evenly distributed over the different seasons. The annual mean windspeed is approximately 12 m/s. The monthly means never drop below 8 m/s, while every single month the maximum windspeed exceeds 30 m/s. Therefore, this region is called the "roaring forties", although these terms were minted for the oceanic environment. From 42° S on southward, Patagonia belongs to the "roaring forties".


Due to this pronounced dominance of west winds, 75%, local wind phenomena like sea or valley winds are most of the time overshadowed. These year-round strong winds put the vegetation in Patagonia under stress due to enhanced evapotranspiration. In contrast to the precipitation there is no pronounced difference in the wind regime due to the Andes.

Rainfall: Rainfall is lower than in other climates as the sector is protected by the Andes. The rainfall in the region is decreasing towards the east, from 2,000 to approximately 600 mm per year, with seasonal fluctuations that gradually sharpen.

There is no predominant depression in west-east direction in this part of the Andes, the precipitation regime is very strongly divided in Patagonia: a western part and an eastern part from the Andes to the Atlantic coast with very little precipitation, reaching 500 mm/a at most.

If following a transect through Patagonia from west to east, it can be observed that over a distance of only 60 km from the main cordillera to the eastern foreland the annual means drop from 5.000 mm/a at the low end to 500 mm/a at the most. Along this very short distance the precipitation regime changes therefore from fully humid to semi-arid. In accordance to this strong gradient the change in vegetation cover from Magellanic Rainforest to Patagonian steppe is observed in merely 25 km.

For all of Patagonia the cloud cover is extraordinary high, with a mean of 5/8.

Temperatures: Temperatures are generally low, January having the highest and July the lowest temperatures. In winter, temperatures normally fall below 0 ° C, with frequent snowfall. In summer, high temperatures attributed to the effect of continentality, are attenuated by strong winds blowing from the mountains. Average annual temperatures vary around 9 ° C, with an increase of temperature range. The highest thermal fluctuation registered between the hottest and the coldest month is of about 12 º C, and average temperatures are 1 to 2 ° C lower those of the the climate in the western part of the region.

In Aysen the cold is a strong limiting factor, reducing the warm season to 4-5 and sometimes just to 2-3 months only.

The influence of the cold pacific air masses and the almost ubiquitous cloud cover leads to a rather small mean daily and yearly temperature amplitude of around 5° C. The daily and yearly variations of the mean and absolute extreme temperatures get more pronounced to the east. This is due to the distance to the Pacific and therefore a more continental component. This leads to a better thermal situation for the eastern part in the summertime, while in the wintertime this is reversed.

While the Antarctic sea-ice reaches its maximum extent in winter, it slowly recedes in spring and quickly extends in fall due to diminishing daylight. This leads to the late arrival of summer and its early termination. The main influence of the Antarctic continent is that to the west of Patagonia, over the Pacific, cyclones are built, which accommodate the cold air masses of Antarctica and drive them towards the Andes. These cold air masses get slightly warmer while being transported over the Pacific and are responsible for the Antarctic influence on Patagonia. During these situations however, they then have a strong influence on eastern Patagonia due to the absence of heating over the Pacific.

This leads to the situation that frost can occur east of the Andes at any time in the year and cause critical damage to the vegetation cover. There are only small seasonal changes in the temperature regime in contrast to the same latitude in the northern hemisphere, but "all the seasons can be observed in a single day” which is absolutely true in valley Leones.

We registered in Pichimahuida:


The strongest wind was 71 m/s - just a gust.

It is not unusual to have sustained winds of 20 -25 m/s.


There were extreme rain events in August 2010 and again in May 2011, resulting in with floods and landslides.


Links to weather conditions in nearest towns:


Puerto Rio Tranquilo

Puerto Guadal

flood in Leones
landslide in Leones

landslide in Leones valley 2011

flood in Leones valley 2010