Aconcagua's climbing season runs from November 15 to March 15. Within that four-month window, weather conditions vary significantly — and weather is the primary factor in whether you summit. The route is not technical. The altitude is manageable with proper acclimatization. But a sustained 100+ km/h wind at 6,500m will stop everyone regardless of fitness or experience.

Here is what the data and climber experience show about each month of the season.

Month-by-month overview

MonthBase camp temps (4,370m)High camp temps (5,950m)Summit temps (6,961m)Typical wind (summit)PrecipitationDaylight hoursSummit window probability
November-5°C to +10°C-15°C to -5°C-25°C to -15°CFrequent high windsModerate snowfall~14.5 hrsLower — early season instability
December-3°C to +12°C-12°C to -3°C-22°C to -12°CVariableDecreasing~15 hrsModerate — improving through month
January0°C to +15°C-10°C to 0°C-20°C to -10°CGenerally lowerLow~14.5 hrsHigher — peak stability period
February-2°C to +13°C-12°C to -2°C-22°C to -12°CGenerally lowerLow, increasing late~13.5 hrsHigher — often underrated
March-5°C to +8°C-18°C to -8°C-28°C to -18°CIncreasingModerate to high~12.5 hrsLower — narrowing windows

All temperatures are approximate ranges based on climber reports, guided expedition data, and weather station records from the region. Actual conditions vary year to year. Wind chill at summit altitude can push effective temperatures to -40°C to -50°C even on "moderate" wind days. (Source: Centro Cultural Argentino de Montaña)

November: early season

The season opens November 15. Snow from the preceding winter may still cover sections of the route above 5,000m. Temperatures are colder than the mid-season months, and weather systems tend to be less settled.

Advantages: Fewer climbers. If you value solitude on the mountain, November offers it. Permit fees are in the low-season tier (Nov 15 – Dec 14), saving roughly $300–350 USD for foreign climbers. (Source: Aconcagua Provincial Park tariff page)

Disadvantages: More variable weather. Snow on the route above high camp can slow progress and add complexity (crampons may be needed earlier). The base camp medical team and ranger presence may be smaller in the early weeks. Summit windows are less frequent.

Who climbs in November: Experienced mountaineers comfortable with colder conditions and willing to accept more weather uncertainty in exchange for a quieter mountain.

December: the season builds

December is transitional. Early December can still feel like late spring at altitude — unsettled weather, lingering snow — but conditions improve steadily through the month. By mid-December, the route is typically well-established and base camps are fully staffed.

December 15 marks the transition from low-season to high-season permit pricing.

Advantages: Less crowded than January. Weather improves week by week. Long daylight hours (~15 hours).

Disadvantages: Early December weather can be unpredictable. The route may not be fully broken in above 6,000m.

Who climbs in December: Climbers targeting a late-December or early-January summit, arriving early enough for thorough acclimatization. Many guided expeditions depart in mid-December, timing their summit attempts for late December or early January.

January: peak season

January is when most people climb Aconcagua. Guided operators concentrate their expeditions here. The weather is generally the warmest and most stable of the season. Base camp is at its busiest — Plaza de Mulas becomes a small city of tents, dining domes, and hundreds of climbers.

Advantages: Warmest temperatures across all elevations. Longest established weather data for this period. Full ranger and medical staffing. All base camp services operational.

Disadvantages: Crowds. On good-weather summit days, queues form at the Canaleta (the steep scree gully at ~6,700–6,900m). This means waiting in extreme cold, losing body heat, and adding hours to an already long day. Camp sites at Nido de Cóndores and Cholera/Berlín can be packed. The "communal" atmosphere is not for everyone.

The January question: Many guides and websites state that mid-January is the "best" time. The data does not support this as a hard rule. January has the highest concentration of climbers and guided groups, which means the most summit attempts — and therefore the most reported summits. This can create an impression of superior weather that is partly a function of sample size. Good weather windows occur throughout the January–February period. (Source: MDZ Online, Jan 2024; climber reports cross-referenced with guided expedition calendars)

February: the underrated month

February deserves more attention than it gets. Climber reports and guided expedition data suggest that early-to-mid February often produces summit windows as stable as — or more stable than — late January. Several seasons have seen the longest calm periods of the year occur in the first two weeks of February.

Advantages: Significantly fewer climbers. Lower-season permit pricing returns on February 1, saving $300–350 USD. Weather can be excellent, particularly in the first half. No queues at the Canaleta. Camps are less crowded. The experience is quieter and more spacious.

Disadvantages: Days are getting shorter (~13.5 hours of daylight vs. ~15 in December). Late February sees temperatures drop and the risk of large storm systems increases. The probability of extended bad-weather holds rises through the month.

Who climbs in February: Climbers who have done their research and are comfortable with a slightly wider range of possible outcomes. Also a good choice for those who started acclimatization in the Cordon del Plata range in mid-to-late January and enter the park in late January or early February.

March: closing the season

March is the end of the line. The season closes March 15. Days are short, temperatures are falling fast, and the viento blanco becomes more frequent. Major storm systems — heavy snow, sustained high winds — are more likely.

Advantages: Very few climbers. The mountain is quiet.

Disadvantages: Shortened weather windows. Colder temperatures at all elevations. If a storm pins you down for 3–4 days, you may not have enough season left for another attempt. Ranger and medical services begin winding down.

Who climbs in March: Very experienced climbers who are already acclimatized (perhaps from another peak or an earlier attempt) and can move quickly when a weather window opens.

Viento blanco: Aconcagua's signature weather event

The viento blanco — "white wind" — is not a storm in the traditional sense. It is a phenomenon specific to high peaks in the Andes where extreme winds at altitude create a white-out of blowing snow and ice crystals, even when the sky may appear clear from below.

How it forms

The Andes sit at the boundary between Pacific maritime air masses and the continental atmosphere of Argentina. When strong westerly winds (the roaring forties and fifties) accelerate over and around Aconcagua's summit, they can reach sustained speeds of 100–150+ km/h. These winds pick up snow from the upper slopes and create a dense, freezing cloud that envelops the upper mountain.

How to recognize it

The classic visual indicator is a lenticular cloud (a smooth, lens-shaped cloud) sitting over or downwind of the summit. From base camp or high camp, this cloud is visible even in otherwise clear conditions. Local guides and the base camp medical team treat a lenticular cap as a definitive no-go signal for summit attempts. (Source: Centro Cultural Argentino de Montaña)

Why it matters

The viento blanco can arrive within hours and persist for days. Sustained winds above 80–100 km/h make upward progress impossible and can make even holding position in a tent dangerous. Wind chill during a viento blanco event can push effective temperatures below -50°C at summit altitude. Several fatalities on Aconcagua have been attributed to climbers pushing into or being caught by viento blanco conditions.

The practical implication for planning: you cannot schedule around the viento blanco. You can only build enough contingency days into your itinerary (at least 2–3, ideally more) to wait it out. Weather forecasts are useful for 48–72 hours ahead but cannot predict wind events a week out with any reliability.

Summit window probability — data, not dogma

There is no official, publicly available dataset from the park service that tracks summit success rates broken down by date. The government does not publish this data. What we have instead is a composite picture from:

Based on these sources, the broad pattern is:

The honest answer to "when should I go?" is: target a summit attempt somewhere in the January 10 – February 10 range, with enough contingency days on either side to accommodate weather. Climbers who enter the park in mid-December with a 20-day itinerary are well-positioned for this.

Visibility patterns

Clear-sky visibility above 5,500m is exceptional on calm days — you can see across the Andes into Chile and pick out distant peaks. But visibility deteriorates rapidly when weather moves in. Cloud formation on Aconcagua tends to follow a daily pattern during stable periods:

This pattern is why summit day starts between midnight and 4:00 AM — to reach the summit during the morning calm window and descend before afternoon weather deterioration.

Base camp medical monitoring and weather

The medical team at Plaza de Mulas does more than check oxygen saturation. They also serve as an informal weather information point. Doctors and rangers receive satellite weather updates and share conditions with climbers. During periods of uncertain weather, the medical team may advise against ascending — this is advisory, not mandatory, but worth heeding.

The rangers and rescue patrol (Patrulla de Rescate de la Policía de Mendoza) monitor conditions at all camps during the season. Recent reporting has raised concerns about budget constraints affecting rescue helicopter availability and staffing levels. The service remains professional and functional, but climbers should not assume unlimited rescue capacity in severe weather. (Source: MDZ Online, Jan 2024; Source: El Sol, Dec 2023)

Planning for weather: practical takeaways

  1. Build contingency days. A 14-day itinerary with zero flex is a recipe for failure or dangerous decision-making. 18–21 days gives you room to wait.
  1. Watch the lenticular cloud. If you see a smooth, lens-shaped cloud over the summit, do not go up. Period.
  1. Do not fixate on a calendar date. The summit window is a weather event, not a schedule. Teams that succeed are teams that are acclimatized, positioned at high camp, and patient enough to wait for the right 48 hours.
  1. February is legitimate. If your schedule allows it, entering the park in late January and targeting a summit attempt in early February puts you in a historically favorable window with fewer people on the mountain. You also benefit from low-season permit pricing.
  1. Morning is your friend. On summit day and on every move between camps, start early. Weather on Aconcagua tends to deteriorate through the day. The calm window is dawn to late morning.
  1. Bring gear for the worst case. Even in January, summit temperatures can reach -30°C with wind chill below -50°C. Your gear list should be built for the worst plausible day, not the average one.

Sources