Look at a wind map of the world and the south of the planet has a whole band, around Antarctica, where the air runs west to east without stopping. Those are the Southern Hemisphere westerlies. Patagonia sits inside that band: El Chaltén is at 49 degrees south, in the middle of what sailors called the “furious fifties”.
Reason 1: the pressure difference
Near 30 degrees south, over the Pacific, there is an almost permanent anticyclone: sinking, warming, high-pressure air. Near 60 degrees, ringing Antarctica, there is a chain of low pressure. Air runs from the high to the low, and the Earth’s rotation bends it eastward. That pressure difference is huge and constant: that is why the west wind is not an event, it is the normal state.
Reason 2: no land to slow it
Between 45 and 55 degrees south, all the way round the world, there is almost no land: it is the only place on the planet where the wind can circle the globe over the sea, with no mountains or continents to take energy out of it. The only thing in the way is the south of South America. New Zealand and Tasmania sit a little further north. Patagonia receives that wind with everything it gathered crossing the Pacific.
Reason 3: the Andes and the ice
Pacific air arrives loaded with moisture and meets the range and the Southern Patagonian Ice Field, some 12,000 km² of ice. It rises, cools, drops rain and snow on the Chilean side and over the ice, and crosses to the Argentine side drier, warmer and sped up by the descent. It is the foehn effect, the same as in the Alps, but here it happens almost every day. Where a valley narrows the air squeezes even more: that is why town can be calm while gusts on the Laguna de los Tres moraine pass 80 km/h.
How much is “so much”
- 49 % of days
- pass 60 km/h gusts at the height of Laguna de los Tres, ten-year average.
- 36 days a year
- with gusts over 100 km/h up high.
- 166 km/h
- the strongest gust we have on record: 3 June 2020.
- 67 km/h against 50 km/h
- the average daily peak gust in January, the windiest month, and in May, the calmest.
In town the wind is half what it is up high. Never judge the day from the hotel window: check the forecast at the height of the hike.
The live wind map, the wind on the trail right now and the full guide to the Patagonian wind: Read more →
Questions
Is Patagonia the windiest place in the world?
It is among the windiest inhabited places, with Tierra del Fuego, the subantarctic islands and Wellington in New Zealand. On the coasts of Antarctica the wind is stronger still, but nobody lives there.
Why does the wind always come from the west?
Because air runs from the Pacific anticyclone towards the low pressure ringing Antarctica, and the Earth’s rotation turns it eastward. In the Southern Hemisphere, between 40 and 60 degrees, that is the normal wind all year round.
Is it windy every day in El Chaltén?
No. 49 % of days pass 60 km/h up high, but the rest are normal or calm days, and autumn brings whole calm weeks. What you cannot have is more than three or four days of notice.
Why does it rain on the Chilean side and not on the Argentine side?
The Pacific moisture is dropped on the climb over the range. What crosses to the east comes down dry. 100 km from the ice it is already steppe.