The weather in El Chaltén

A climate with character

Bright sun, a gentle breeze, strong winds, on-and-off rain and even a surprise snow flurry in the middle of summer: sometimes all of it happens in a single day. Patagonian weather is famous for its temper, and it's an inseparable part of your adventure in El Chaltén.

It isn't a backdrop; it's part of the story. A day can start out calm, with Fitz Roy glowing pink above a still valley, and by afternoon bring racing clouds, drizzle blowing in sideways and sunshine again before dinner. The mountains catch the moist wind from the Pacific and send it back as gusts, clear spells and curtains of rain.

The name says it all: in the Aonikenk language, Chaltén means "smoking mountain." The clouds that catch on the granite spires and drift off a few minutes later are the area's signature show. A clear view of Fitz Roy isn't guaranteed: you have to wait for a window of good weather. That's why it pays to stay more than one night; give it two or three days and it almost always appears.

Average high Average low Daylight hours

The word that sums up the weather in El Chaltén is "unpredictable."

And yet, glorious days with clear skies and little wind are more common than its reputation suggests. The weather's character isn't a threat: it sets the pace you hike at.

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The weather right now

National Parks webcam in El Chaltén, facing northwest. Press play to see how the day has unfolded. Via Windy.

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Forecast for the coming days

Before heading out on a trail, check the wind and gust forecast: in El Chaltén it matters more than the temperature.

Wind, gusts, temperature and wind chill, cloud cover and rain for the next 10 days. Forecast by Windguru.

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Get ready for Patagonian weather

The wind is an unavoidable presence, especially between October and March, although it can show up in any month of the year. In the southern summer, from December 21 to March 20, windless days are rare. There's no need to fear it, but you do need to understand it: it's the star of the trip, the soundtrack of the trails and the reason Fitz Roy shows itself and then hides again.

In spring and summer, gusts of 60 to 80 km/h (37 to 50 mph) are common on exposed stretches, and a 14 °C (57 °F) day with strong wind feels much colder. In town you notice the wind; on the moraine, you hear it too.

Morning is the calmest time of day. The wind usually picks up by mid-morning and strengthens in the afternoon, so long hikes are best started early: not just because of the distance, but also to make the most of that calm window.

Sudden temperature changes, thick cloud and rain or a snow flurry on a day that dawned sunny are all part of the trail. So always set out with warm and waterproof layers, even if the sky looks perfect. Rain rarely forces you to call off a hike: what decides whether the long trek is worth it is the wind and low cloud. A twenty-minute drizzle, several times a day, is normal.

Solar radiation is intense at these latitudes, even on cloudy days. A hat, sunscreen and sunglasses belong in your pack all year round (more on protecting yourself from the sun below).

What to wear

What works is dressing in layers, not wearing a city coat:

• A base layer that isn't cotton: it has to keep you warm even when it gets wet.
• A fleece or mid-layer for the forest and for breaks.
• A waterproof, windproof jacket: it's the most important item on the trip, even in January.
• A light hat, thin gloves and a neck gaiter: they take up almost no space and make all the difference on a windy summit.
• Hiking boots with good grip: Patagonian mud is part of the trail, not an accident.

Season by season

In summer you don't need high-mountain gear for the classic trails, but you do need to be able to add or remove a layer without thinking twice. In autumn the lenga forest turns red, there are fewer people and the wind eases, although mornings call for more warm layers and the days get shorter. In winter the town goes quiet, the snow settles in from June to August, and some trails require prior registration and technical gear. Spring brings the wind back and the valley gradually opens up.

Before you set out

Two checks are enough: the trail report at the National Park Visitor Center, at the entrance to town, and a gust forecast. Trail conditions tell you more than the color of the sky.

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The sun is stronger than it feels

In El Chaltén, the cool air and the wind are deceptive. You can hike in a jacket with cold hands and come back from the trail with a sunburned face and neck. The sun here doesn't feel as hot as it does at the beach, but it burns just as much or more, precisely because it gives no warning.

UV radiation peaks between 1 and 3 p.m. On a clear summer day, the UV index reaches very high and, on some days, extreme. You don't need a picture-perfect sky, either: a thin layer of cloud lets much of the radiation through. And in spring, when the edge of the ozone hole sometimes reaches southern Patagonia, the index can climb even higher, even under an overcast sky.

From December to March, the rule is simple: always wear sunscreen from 10 a.m., and protect yourself from the sun until 6 p.m. Those eight hours cover the whole window of strong radiation, not just midday. Before 10 a.m. and after 6 p.m. the index drops; in between, on a long hike, don't trust the sky.

On the trail, the sun also bounces back. Granite, lake water and snow reflect the radiation onto your face, the back of your neck and your eyes. That's why a hike to Laguna de los Tres or Laguna Torre, with long stretches in the sun, calls for more care than an afternoon in town.

There's no need to avoid the middle of the day: just head out prepared and stop worrying about it.

• Broad-spectrum sunscreen, SPF 30 or higher: put it on before 10 a.m. and reapply at breaks, especially if you're sweating or it's drizzling.
• Lips, ears, the back of your neck and the backs of your hands: these are the spots people forget most.
• A hat with a brim or visor: a running cap leaves your neck and ears exposed.
• Sunglasses with UV protection: the wind already tires your eyes, and the glare off water and snow even more. Without a filter, the midday sun can leave your eyes irritated by the end of the day.
• A light long-sleeved top, if the heat allows: it protects better than sunscreen and, if it's made of technical fabric, it's no warmer than a T-shirt.

The lenga forest offers real shade. The trouble starts when the trail comes out onto a moraine, a lake or the final granite stretch: that's when you want your hat within reach, not at the bottom of your pack.

A cool, cloudy day is not a low-UV day. At this latitude, the sun doesn't feel like much but does a lot. From December to March, between 10 a.m. and 6 p.m., protecting your skin and eyes is part of your gear, just like your windproof jacket: it takes up little space and changes how you come back from the trail.

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The town and the valley have different weather

The town sits at about 400 meters (1,300 ft) above sea level, in the Río de las Vueltas valley, where the rock walls and trees offer some shelter. On a January midday you can head out in a T-shirt and come back at night in a jacket.

As soon as you enter the forest, everything changes. Under the lengas the wind eases and the trail feels warmer and more humid. When you reach a lake, a moraine or the last kilometer up to Laguna de los Tres, the valley opens up and the wind returns in full force. Up there, the temperature in town is no longer a useful guide: there's more altitude and more exposure, and in almost any month it can snow above the tree line. On cold days it can snow at the base camps while it only drizzles in town.

When you hike up to a viewpoint, keep this rule of thumb in mind: the temperature drops roughly 1 °C for every 100 meters you climb (about 5.5 °F per 1,000 ft). Laguna de los Tres, for example, sits at about 1,170 meters, almost 800 meters above town: even if it's 15 °C (59 °F) down below, it can be under 10 °C (50 °F) up there, and with the wind it feels much colder.

Heading west, as you get closer to the Southern Patagonian Ice Field, the air becomes more humid and colder. A granite slab in the sun can feel hot, but in the shade and in the gusts you'll need the layer that felt like too much an hour earlier.

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If you're camping

The campgrounds in town have shelter, restrooms and a roof nearby. Inside the National Park, though, the night is very different. Exposed sites near lakes and moraines are colder and windier than town; sites in the forest are calmer but damper. Your tent has to withstand gusts, not just rain: a loose stake will find out before you do.

It's worth sleeping warmer than seems necessary: the overnight low in town is already chilly, and in the valley it drops even further. Choose your sleeping bag for the real nighttime temperature, not the midday one. Cook before the wind picks up and stow anything lightweight. Stream water is excellent, and ice-cold. In summer there's so much light that you eat dinner in the sun; in June, by contrast, the sun sets before 6 p.m.

Camping here isn't about enduring the weather: it's about falling asleep to the murmur of the valley and waking up to see whether the mountain has decided to show itself.

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Daylight, the other luxury

At this latitude, day length changes a lot over the year. In December there are about 16 hours of sun above the horizon, and the long Patagonian twilight stretches the light even further: you can hike comfortably past 10 p.m. In June, the day lasts just over 8 hours. That's why summer lets you head out at sunrise and fit in another short hike in the afternoon, while in winter you have to pick a single window.

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Temperatures

During the busiest months, from October to April, temperatures in town are mild, and in January and February you can expect fairly warm days. But don't let your guard down: at night the temperature can easily drop to 5 °C (41 °F) or lower.

The figures shown here were recorded at town level. On the trails, subtract a few degrees and add a layer.

In January and February, the average values are:

• low: 7.5 °C (45.5 °F)
• mean: 13.3 °C (56 °F)
• high: 19 °C (66 °F)

Looking at weather records over recent decades, you would see wide swings between absolute highs and lows, and in when during the year they occurred. For example, there is a record high of 31.6 °C (88.9 °F) in February 2003 and a record low of −20.0 °C (−4 °F) in July 2001.

Month by month

Approximate temperatures in town. Astronomical daylight hours at 49° S, not counting twilight. Wind lowers the perceived temperature.

All climate records were provided by the Lago Viedma ranger station of Los Glaciares National Park.