Chile Braces for Extreme Rain: These Regions Will Be Most Affected

El Ciudadano

Original article: Chile enfrentará lluvias extremas estas serán las regiones más afectadas

An intense atmospheric river and a series of frontal systems are set to bring persistent rainfall from Tuesday through Thursday. Meteorologists warn that central-southern regions could see accumulations exceeding 300 millimeters of rain, significantly increasing the risk of flooding, river overflow, landslides, and connectivity disruptions.

This report serves as a preventive measure.

Chile is gearing up for one of the most significant meteorological events of winter 2026. Multiple forecasting models agree on the arrival of a large frontal system, reinforced by an atmospheric river transporting vast amounts of moisture from the Pacific Ocean to the central and southern regions of the country.

According to analyses from the ECMWF and GFS numerical models, rainfall will begin to intensify on Tuesday, peak on Wednesday, and continue into Thursday, particularly affecting the regions of Valparaíso and Biobío.

Experts explain that this phenomenon is not a conventional cold front. The interaction between an atmospheric river, a deep low-pressure system, and the jet stream will ensure that moisture supply remains steady for several hours, facilitating continuous and intense rainfall.

Regions at Highest Risk

The most significant impact is expected in the regions of Maule, Ñuble, and Biobío, where precipitation levels may reach exceptional heights, especially in precordilleran and mountainous areas.

Current estimates indicate the following expected rainfall accumulations for the period from Tuesday to Thursday:

Region	Estimated Accumulation
Coquimbo	5 to 30 mm
Valparaíso	25 to 70 mm
Metropolitana	50 to 90 mm
O’Higgins	60 to 100 mm
Maule	80 to 130 mm
Ñuble	90 to 150 mm
Biobío	80 to 140 mm
La Araucanía	70 to 120 mm
Los Ríos	60 to 100 mm
Los Lagos	50 to 80 mm

However, conditions change significantly in the precordillera and mountainous regions.

In these areas, models project considerably higher accumulations:

Metropolitana: between 120 and 200 mm.
O’Higgins: between 120 and 200 mm.
Maule: between 180 and 260 mm.
Ñuble: between 220 and 340 mm.
Biobío: between 180 and 300 mm.
La Araucanía: up to 250 mm.

The highest totals could be concentrated in mountainous sectors of Ñuble and Biobío, where the persistence of the atmospheric river could push totals above 300 millimeters.

Wednesday Will Be the Most Challenging Day

The peak concern is expected to be on Wednesday.

On this day, the atmospheric river is anticipated to reach its maximum intensity while the frontal system remains nearly stationary over central-southern Chile.

This scenario will likely favor persistent rainfall for much of the day, accompanied by strong winds and heavy snowfall in the mountains.

In coastal and mountainous areas, wind gusts could exceed 80 km/h.

Santiago Also to Receive Significant Rainfall

The Metropolitan Region will not be spared from this event.

Models project between 50 and 90 millimeters for much of Santiago, while precordilleran communes like San José de Maipo could exceed 120 millimeters significantly.

Although these figures may still vary based on the eventual trajectory of the frontal system, they represent a volume sufficient to cause urban flooding, rises in stream levels, and challenges to road infrastructure.

Risk of Flooding and Landslides

Beyond the total amount of rain, one of the top concerns for specialists is the intensity of the precipitation.

In some areas of Maule, Ñuble, and Biobío, rainfall rates could exceed 10 or even 20 millimeters per hour, a threshold typically associated with flash floods, creek activation, and landslides.

This is compounded by partial snowmelt in mountainous areas and the progressive saturation of soils, factors that heighten hydrological risk.

A Phenomenon Driven by an Atmospheric River

Atmospheric rivers are corridors of water vapor that carry massive amounts of moisture from tropical and subtropical regions to mid-latitudes.

When these systems impact the Andes Mountains, the humid air rises, cools, and produces intense precipitation that can last for many hours.

In this instance, models indicate a high-intensity atmospheric river, explaining the forecast for abundant rainfall across much of the central-southern region of the country.

Call to Action for Prevention

Authorities have strengthened monitoring of major waterways, reservoirs, and historically flood-prone areas. However, specialists recommend that the public stay informed through official channels, avoid unnecessary travel during periods of peak storm intensity, and take precautions in areas near rivers, creeks, and unstable slopes.

While forecasts will continue to adjust in the coming hours, there is broad consensus among meteorological models that Chile will face a high-magnitude precipitation episode, particularly in the central-southern area, where some localities could experience one of the most significant rainfall events of this winter.

Timeline of the Storm: When to Expect the Worst

Tuesday, July 14

06:00 – 12:00 hours

Rainfall begins in Los Lagos, Los Ríos, and La Araucanía.
The first winds associated with the frontal system arrive.

12:00 – 18:00 hours

Rain intensifies over Biobío and Ñuble.
Significant snowfall is recorded in the central-southern mountains.
Wind increases in coastal areas with gusts of between 50 and 70 km/h.

18:00 – 24:00 hours

The front reaches Maule.
Continuous rainfall consolidates between Biobío and Maule.
Soils start to saturate in precordilleran areas.

Wednesday, July 15 (Day of Peak Intensity)

00:00 – 06:00 hours

The atmospheric river reaches its maximum moisture supply.
Intense rain occurs from Maule to La Araucanía.
The highest snowfall of the event is reported in the mountains.

06:00 – 12:00 hours

Highest precipitation rates are expected.
In sectors of Maule, Ñuble, and Biobío, rates may exceed 10 to 20 mm per hour, increasing the risk of flash floods and creek rises.

12:00 – 18:00 hours

The storm reaches its maximum extent.
Persistent rain continues between O’Higgins and Los Ríos.
Wind gusts could exceed 80 km/h in coastal and mountainous areas.

18:00 – 24:00 hours

The system begins to slowly shift northward.
Strong rains continue in Maule, Ñuble, and Biobío.

Thursday, July 16

06:00 – 10:00 hours

The front fully reaches the central zone.
Rain begins in Valparaíso and inner parts of the Metropolitan Region.

12:00 – 18:00 hours

Rain becomes widespread in Santiago.
In precordilleran communes, the risk of mudslides increases due to the combination of intense rain and low zero isotherm.

18:00 – 24:00 hours

The capital and much of the Metropolitan Region are expected to experience the period of highest intensity.
Significant rainfall will also be recorded in Valparaíso and O’Higgins.
By early Friday, the system will begin to gradually weaken over the central area.

Critical Hours of the Event

If the projected evolution from meteorological models holds, the highest risk windows will be:

Tuesday: between 18:00 and 24:00 hours in Maule, Ñuble, and Biobío.
Wednesday: between 03:00 and 18:00 hours, when the atmospheric river could reach its maximum intensity over the central-southern area.
Thursday: between 15:00 and 23:00 hours in Valparaíso and the Metropolitan Region, where the most intense rains are projected for the capital.

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