A series of unusually powerful cutoff-low storms brought snow reaching from the Andes almost to Chile’s Pacific coast in August 2026, forcing major astronomical observatories offline and causing damaging floods and mudflows across northern Chile, against the backdrop of a strengthening El Niño.
Parts of the Atacama Desert — among the driest places on Earth, with some sections receiving less than a millimetre of rain in an average year — were blanketed in snow through August 2026, following a series of unusually powerful winter storms. NASA Earth Observatory imagery, drawing on Landsat and MODIS satellite data and reported in a feature published 1–2 September 2026, documented snow cover extending from the high Andes across the hyperarid heart of the Atacama and reaching nearly to the Pacific coast near the port city of Antofagasta — a spatial extent well beyond what the region typically sees even in its rare snow years.
The storms were driven by cutoff lows — low-pressure systems that separate from the main jet stream and occasionally wander into northern Chile, according to René Garreaud, an atmospheric scientist at the University of Chile, who noted that a similar mechanism produced the region’s previous notable snowfall event in 2025. What distinguished the late-August 2026 event, Garreaud explained, was that the cutoff low that produced it spun off from an unusually large trough — an elongated area of low pressure spanning an enormous stretch of the hemisphere, from the southern tip of South America into the subtropics — combined with ample coastal moisture, producing a wetter and more widespread event than the comparatively localised 2025 snowfall.
Observatories forced offline, floods and mudflows on the ground
The Atacama’s extreme dryness and high elevation are precisely what make it one of the world’s premier sites for ground-based astronomy, hosting the Atacama Large Millimeter/submillimeter Array (ALMA) and several other major observatories on the Chajnantor Plateau and nearby high-altitude sites. Some of these facilities suspended operations during the storm sequence to protect sensitive equipment from snow and wind loading — a now-recurring operational disruption for the region’s observatories, which have had to activate emergency “survival mode” protocols, including reorienting antennae away from the wind, during comparable events in the past two years. Beyond the mountains, the storms’ abundant precipitation triggered destructive mudflows and flash flooding at lower elevations across northern Chile; Chile’s National Disaster Prevention and Response Service (SENAPRED) reported thousands of people affected and hundreds of homes with major damage, alongside road closures, power outages and landslides in some communities.
Part of a pattern, not an isolated event
This is not the first time in recent years that the Atacama has seen anomalous snowfall — a comparable, though more localised, event occurred in 2025 — and NASA’s reporting explicitly situates the August 2026 storms against the backdrop of a strengthening El Niño, the periodic warming of central and eastern tropical Pacific waters that reliably alters weather patterns across South America, generally increasing precipitation in parts of the continent’s western coast. Whether this specific storm sequence should be attributed primarily to El Niño’s influence, to the particular atmospheric trough configuration Garreaud described, or to some combination of the two remains a matter for further meteorological analysis; NASA’s reporting notes the El Niño context without asserting a fully worked-out causal attribution.
Why it matters
Events that disrupt one of the world’s driest and most astronomically important regions carry consequences well beyond local weather curiosity. Repeated observatory shutdowns — now occurring in successive years — raise practical operational questions for facilities like ALMA about how frequently extreme-weather contingency protocols will need to be invoked going forward, and whether infrastructure designed for a historically hyperarid climate needs reassessment as anomalous precipitation events recur. On the ground, the flooding and mudflow damage in normally water-scarce communities illustrates a broader pattern seen elsewhere in extremely dry regions: infrastructure, drainage systems and settlement patterns built around the assumption of near-total aridity are often poorly equipped to handle sudden, concentrated precipitation when it does arrive, which can make rare wet events disproportionately damaging compared with the same rainfall total falling in a region built to handle regular rain. For a hyperarid region increasingly experiencing anomalous winter storms in consecutive years, this event adds another data point — though not, on its own, definitive proof — to a broader conversation about shifting precipitation patterns in traditionally extremely dry parts of the world.
-Raja Aditya
Key facts
- Rare, unusually widespread snowstorms hit Chile’s Atacama Desert through August 2026, with snow extending from the Andes to near the Pacific coast
- Driven by a cutoff low spun off from an unusually large hemispheric-scale pressure trough, combined with ample coastal moisture; occurred against the backdrop of a strengthening El Niño
- Several major astronomical observatories, including facilities on the Chajnantor Plateau, suspended operations to protect equipment
- Triggered destructive mudflows and flash flooding at lower elevations; SENAPRED reported thousands affected and hundreds of homes with major damage
- Reported via NASA Earth Observatory feature, 1–2 September 2026, using Landsat and MODIS satellite imagery
