The Andean Winter: What Happens on Ojos del Salado When the Climbers Leave

When the expeditions end, the mountain’s real story begins.

Every year, somewhere between late March and April, a silence descends over the slopes of Ojos del Salado. The last 4x4s roll back toward Copiapó. The last crampons are packed away. And the highest active volcano on Earth is left to itself again. For most of the world, this is the off-season. For the mountain, it is anything but.

Understanding what happens on Ojos del Salado during the Andean winter is not just a matter of curiosity. It is, for anyone serious about a future ascent, the beginning of a strategy.

The Season Ends. The Mountain Does Not.

Between May and October, the Southern Andes enter a period of intense meteorological activity. For Ojos del Salado specifically, this translates into sustained winds exceeding 100 km/h across the upper flanks, temperatures that regularly drop below -30°C at the summit, and snowfall events that reshape the mountain’s terrain from one week to the next.

The famous crater lake — one of the world’s highest bodies of water — freezes over entirely. The volcanic vents that give Ojos del Salado its fumarolic character slow their activity under the weight of ice. The route markers established during the previous season are buried. The mountain, in a very literal sense, resets.

This is not a passive process. The winter does not simply pause the mountain. It rebuilds it.

A Landscape That Rewrites Itself

Dawn from the upper slopes. In winter, the mountain rebuilds itself in silence.

One of the least understood aspects of Ojos del Salado is that the Atacama context makes it unlike any other 6,000-meter peak. The extreme aridity of the Atacama Desert means that even in winter, precipitation accumulates differently than in the wetter Andean ranges further south. The result is a specific type of freeze-thaw cycle that creates the extraordinary textures — the penitentes, the salt crusts, the sculpted ridgelines — that make this mountain visually unlike anything else in South America.

During winter, the process that creates these formations is at its most active. Wind erosion at altitude is relentless. Frost wedging cracks rock faces. Volcanic heat from below creates temperature inversions that confound the logic of the landscape above. For the mountaineer who will eventually stand at the crater rim, understanding this environment is not academic — it is the foundation of every decision made during the actual ascent.

The Window You Don’t See

The November–March climbing window for Ojos del Salado is not arbitrary. It exists because of a specific meteorological phenomenon: the strengthening of the South Pacific anticyclone, which blocks the frontal systems that batter the peak during winter and creates the sustained periods of calm that make safe ascent possible.

This window is narrow, and within it, the best weather concentrates further. Professional operators with years of data on this specific mountain understand that the difference between a summit and a forced turn-around is often a matter of reading micro-forecasts at altitude — not just weather apps, but cloud formation patterns, wind direction shifts, and pressure gradients specific to the Atacama Puna.

The winter that appears to close the mountain is, in reality, charging it toward that November opening.

The Best Ascents Are Planned in Winter

At HME, the off-season is our busiest planning period. Route assessments are updated based on last season’s terrain changes. Acclimatization schedules are refined. Equipment is inspected, replaced where necessary, and staged at our logistics points in Copiapó. The base camp at Laguna Verde is prepared for the season ahead.

For climbers who will join us from November onward, the equivalent work happens at home. Physical preparation for 6,893m requires a minimum of four to six months of structured training. The high-altitude acclimatization strategy — which mountains to climb beforehand, how many rotations to build into the schedule — must be planned, not improvised.

The mountaineers who summit Ojos del Salado in January started their preparation in July. The ones who arrive in November unprepared do not reach the top. It is that direct.