Key Takeaways
Altitude sets the scene. Air cools with height, so precipitation over very high peaks turns to snow even when nearby lowlands feel mild.
Mountains make clouds. Ranges force moist air upward; rising air cools, condenses, and releases rain or snow depending on temperature.
A vertical contrast in Argentina. Southern ranges can see snow at low levels; in the north, lasting snow mostly clings to very high summits.
Quiet processes shape the white skyline. Light, dry snowfall, wind-drift, and direct vapor-to-ice deposition can make snow seem to “form” on the spot; sublimation slowly removes snow straight to vapor.
Snow is not hail; mirage is not snow. Snow grows as ice crystals in cold clouds and falls gently; hail builds in strong thunderstorm updrafts as layered ice. A mirage is a refraction trick of light, not frozen precipitation.
Story & Details
A common question, a clear answer. The Andes look white from end to end, yet northern cities rarely see snow. Height explains the picture. Many northern peaks rise well above five to six kilometers. At those elevations the air is often below freezing, so precipitation aloft arrives as snow. The average drop of temperature with altitude—the environmental lapse rate—means warm valleys can sit beneath icy summits.
How mountains turn moisture into snow. When wind pushes moist air against a range, terrain lifts the air. As it rises it expands and cools. Water vapor condenses into cloud and then precipitation. If temperatures are below freezing, snow falls onto ridges and cirques. This orographic engine runs along the chain, so even where the climate is dry, peaks can hold white caps.
Why the northern cordillera still looks white. In the high, arid north, snowfall is often fine and sparse. Strong winds move existing snow, building drifts and cornices. Deposition adds fresh rime or frost straight from vapor, so rock faces can gain a thin, bright coat without a dramatic storm. At the same time, sublimation removes part of the snowpack directly to vapor, especially under sun and wind. What endures is the coldest, most sheltered fraction—enough to keep the skyline pale.
Snow versus hail, and a word on mirage. Snow forms quietly in cold clouds as crystals that lock together into flakes. Hail forms violently inside thunderstorms; updrafts carry embryos of ice up and down, adding layers until stones grow heavy and fall—even on warm days. A mirage is different again: sharp temperature layers bend light and trick the eye into seeing water or lifted horizons. None of these effects requires intent. Peaks simply create the conditions that decide what reaches the ground.
Conclusions
Peaks write their own weather. Mountains do not attract snow by choice; by lifting air and living in thin, cold layers, they make snow likely. In southern Argentina, that script can play out close to sea level. In the north, it plays out high above the valleys, where even small, dry falls and wind-sculpted deposits keep the summits white. The view is continuous, but the reason is vertical.
Selected References
[1] Met Office (official channel) — “Different types of rain” (includes orographic rain): https://www.youtube.com/watch?v=dWZ5_0wcYJ0
[2] NOAA National Weather Service Glossary — “Orographic / Orographic Precipitation”: https://forecast.weather.gov/glossary.php?word=OROGRAPHIC
[3] U.S. Geological Survey — “Sublimation and the Water Cycle”: https://www.usgs.gov/water-science-school/science/sublimation-and-water-cycle
[4] National Snow and Ice Data Center — Cryosphere Glossary: https://nsidc.org/learn/cryosphere-glossary
[5] NOAA National Severe Storms Laboratory — “Severe Weather 101: Hail Basics”: https://www.nssl.noaa.gov/education/svrwx101/hail/
[6] Encyclopaedia Britannica — “Andes Mountains”: https://www.britannica.com/place/Andes-Mountains
[7] Oxford Reference — “Lapse rate”: https://www.oxfordreference.com/display/10.1093/oi/authority.20110810105241747
[8] World Meteorological Organization, International Cloud Atlas — “Mirage”: https://cloudatlas.wmo.int/mirage.html
Appendix
Deposition. The phase change where water vapor turns directly into ice on cold surfaces; common on high, windy peaks and a reason rock can glaze white without obvious snowfall.
Environmental lapse rate. The average decrease of air temperature with height in the lower atmosphere, often taken as about 6.5 °C per 1,000 meters; it explains cold summits above warm valleys.
Hail. Solid precipitation grown inside strong thunderstorm updrafts as layered ice; it can fall even when the ground is warm and is distinct from snow in origin and structure.
Mirage. An optical illusion caused by refraction of light through air layers with sharp temperature differences, making distant scenes look shifted, stretched, or watery.
Orographic uplift. The lifting of air as it moves over rising terrain; rising air cools, forms cloud, and produces precipitation—rain below the freezing level, snow above it.
Sublimation. The direct transition of ice or snow to water vapor without melting; strong sun, dry air, and wind at altitude make this process efficient on exposed summits.
My Diary - Leonardo Cardillo 