Snow and 90 km/h (55 mph) winds suspend ALMA observations in the Atacama Desert, Chile
A new snowfall accompanied by winds of 90 km/h (55 mph) reached the Chajnantor Plateau in Chile’s Atacama Desert on August 18, 2026, keeping astronomical observations suspended at the Atacama Large Millimeter/submillimeter Array (ALMA). The antennas remained in survival mode as winter weather continued to affect high-altitude roads, border crossings and communities across northern Chile.
Image credit: JC Rojas, ALMA Photography Ambassador
The latest conditions followed a snowstorm at the array on August 12, when ALMA reported that astronomical observations had stopped and the antennas had entered survival mode. Data provided by the observatory during that episode showed a temperature of −7.91°C (17.8°F) at Chajnantor.
Snow also affected areas around San Pedro de Atacama. Machuca, a high-altitude community north of the town at about 4 000 m (13 100 feet) above sea level, was covered by snow on August 12. Chile’s national police reported snowfall, low temperatures, and ice on mountain roads and maintained preventive restrictions because of hazardous driving conditions, according to Emol.
The police advised motorists against traveling into affected cordillera sectors while the conditions persisted and told drivers to consult official route information before departure. Access to high-altitude destinations around San Pedro de Atacama, including Machuca and the El Tatio sector, was restricted during the first episode.
Winter weather also affected international and regional connectivity. By August 14, high-altitude routes and border crossings in El Loa remained disrupted, with 138 trucks reported stopped in San Pedro de Atacama while waiting for the Jama and Hito Cajón crossings to reopen, according to SoyChile.
Snow was reported farther north along the Calama-Ollagüe corridor on August 16. The police urged motorists to use additional caution because of snow and road conditions.
Chile’s Directorate of Meteorology (DMC) increased its snow-related forecast messaging ahead of the latest conditions. At 20:13 LT on August 16, the agency updated Aviso A422-2/2026, forecasting probable snowfall in parts of Antofagasta and Atacama regions.
At 13:21 LT on August 17, DMC issued Alerta AA143/2026 for moderate snowfall in the Antofagasta precordillera from the Minera Escondida sector southward and in the Atacama precordillera north of Inca de Oro.
In neighboring Atacama Region, Roberto Muñoz, regional director of the National Service for Disaster Prevention and Response (SENAPRED), said after a technical meeting with DMC that snowfall could reach about 25 cm (9.8 inches) per day in cordillera sectors, with total accumulation approaching 1 m (3.3 feet) during the event. Muñoz said the zero-degree isotherm could fall to around 2 400 m (7 900 feet).
Hazardous weather extended beyond the high-altitude snow zones. Coastal communes in Antofagasta Region were placed under Yellow Alert during the broader weather episode, while activation of quebradas prompted SENAPRED evacuation messaging for four sectors of Tocopilla. Rainfall, rockfalls and debris also affected parts of the regional road network.
DMC separately issued Alarma AAA8/2026 for intense precipitation in coastal and Cordillera de la Costa sectors between Tocopilla and Taltal, with 15–25 mm (0.6–1.0 inches) forecast from the early hours through the night of August 18. The coastal rainfall impacts were geographically separate from the snowfall observed at Chajnantor and other high-altitude sectors.
ALMA operates its antenna array at approximately 5 000 m (16 400 feet) on the Chajnantor Plateau.
I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.
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