The OLI (Operational Land Imager) aboard the NASA USGS Landsat 8 and Landsat 9 satellites documented the dramatic change in images taken on August 6 and August 14, before and after a stretch of severe weather, respectively.

The views provide a close look at the Chajnantor plateau within the Altiplano-Puna volcanic complex. This high-elevation area is home to the Atacama Large Millimeter/submillimeter Array (ALMA), one of the most powerful radio telescopes in the world. As heavy snow and strong winds moved through the area, ALMA suspended operations and placed its antennas into a protective survival mode.

Conditions became even more unusual later in the month. A second storm spread fresh snow across a much broader part of northern Chile. An August 19 image from the MODIS (Moderate Resolution Imaging Spectroradiometer) aboard NASA's Terra satellite shows snow reaching westward from the Andes, crossing the hyperarid heart of the Atacama, and approaching the Pacific coast south of the Chilean port city of Antofagasta. Several other major astronomical observatories are located in this coastal region, and some also suspended operations while the storm passed.

An Unusual Atmospheric Setup

Much of the winter precipitation that reaches this part of Chile is associated with cutoff lows, low-pressure systems that separate from the jet stream and can sometimes move into northern Chile. René Garreaud, an atmospheric scientist at the University of Chile, said this type of system was responsible for the notable snowfall in 2025.

A cutoff low was also behind the late August 2026 storm, but this event developed under more unusual circumstances. The system broke away from an exceptionally large trough, an elongated region of relatively low atmospheric pressure, that extended across a huge portion of the Southern Hemisphere from the southern tip of South America into the subtropics.

Combined with plentiful moisture near the coast, this disrupted weather pattern generated precipitation across an exceptionally broad area. Rain and snow fell offshore, along the coastline, through the center of the Atacama Desert, and over the Andes. Garreaud said precipitation totals reached levels "rarely seen in the otherwise extremely arid region."

Months of Rain in Just Three Days

Not all of the precipitation arrived as snow. Along parts of Chile's northern coast, it fell as heavy rain. In Taltal, nearly 40 millimeters (1.6 inches) accumulated over three days. According to Garreaud, that amount is roughly 10 times the city's average annual rainfall.

"We see these kinds of events only a few times, if any, per decade."

The intense precipitation had serious consequences. Mudflows and flash flooding struck parts of northern Chile, causing widespread disruption and damage. The National Disaster Prevention and Response Service (SENAPRED) reported that thousands of people were affected and hundreds of homes suffered major damage.

El Niño Sets the Stage for a Wetter Winter

Garreaud pointed to the strengthening El Niño as an important backdrop to the unusually wet winter unfolding across north-central Chile. The August storms were not the first major events of the season. A major event in July also produced significant impacts in Chile's Norte Chico region.

During El Niño, the subtropical Pacific high, which ordinarily helps maintain dry conditions over the region, becomes weaker. At the same time, a blocking high is more likely to develop over the South Pacific near the southern end of the continent. Together, these atmospheric changes shift the Southern Hemisphere storm track closer to the equator, making it easier for powerful weather systems to reach areas of Chile that are normally extremely dry.