Table of contents

Atmospheric River Storm: Torrential Rain Expected In SoCal and LA

EcoFlow

Table of contents

Meteorologists are predicting a fast-moving atmospheric river storm will land in Los Angeles and Southern California as early as November 13, 2025.

Areas recently devastated by wildfires could be particularly hard hit with four days of heavy rain expected which could cause flooding and debris flow in already struggling or rebuilding areas.

After hitting Northern California on Wednesday, heavy rains could last in SoCal until at least Saturday.

Downtown LA may see more rain over four days than it has since the month of February 2025..

Flooding is a concern but one potential benefit from the atmospheric river storm is a reduced risk of fire and a shorter than expected Autumn wildfire season.

California is famous worldwide for its sunny lifestyle but SoCal is no stranger to rainstorms.

What makes this atmospheric river storm so threatening?

Source: (USGS)

What Is an Atmospheric River?

According to the United States Geological Survey (USGS), atmospheric rivers are "rivers in the sky… that transport water vapor from the tropics towards the poles."

The formation of an atmospheric river begins over the warm ocean waters of the tropics and subtropics, where intense sunlight heats the sea surface and causes massive amounts of water to evaporate into the atmosphere.

The temperatures get so hot that water evaporates and rises into the atmosphere, almost like steam.

A portion of the water vapor circulates away from the equator by forming a narrow band of moisture that flows to faraway locations, much like a river on land.

Comparatively speaking, atmospheric rivers flow close to the Earth's surface, about half a mile to a mile above the ground or sea.

As the vapor flows over coastal areas and inland over mountains, the river is forced upwards.

The water vapor then condenses into rain or snow and falls to the ground.

Depending on the "size" of the atmospheric river, the precipitation can be significant, or even catastrophic.

An atmospheric river-driven mega-storm has been characterized by USGS as having the potential to be the climate equivalent of the Big One — the devastating earthquake scenario feared by scientists and West Coast residents for years.

The ARkStorm Scenario model updated in 2018 found that:

A severe California winter storm could realistically flood thousands of square miles of urban and agricultural land, result in thousands of landslides, disrupt lifelines throughout the state for days or weeks, and cost on the order of $725 billion. This figure is more than three times that estimated for the ShakeOut scenario earthquake, that has roughly the same annual occurrence probability as an ARkStorm-like event.

(Source: USGS)

How Big Do Atmospheric Rivers and Storms Get?

Big.

Really, really big.

Putting the significant differences aside, the USGS calls atmospheric rivers "the largest rivers of fresh water on Earth."

Studies of atmospheric rivers over the Pacific have found that they transport water vapor at a rate equal to 7–15 times the average daily discharge of the Mississippi River. They can be hundreds to thousands of miles long, and though they are narrow in the context of weather systems, "narrow” can mean up to 300 miles across!

Atmospheric river activity worldwide never stops, is mostly benign and frequently beneficial, particularly in locations like California, which often suffer from having too little, not too much, rain.

However, atmospheric river storms also cause an estimated $1 billion a year in Western states and some of the most extreme weather events in California history.

The Great Flood of 1862, which remains the biggest flood on record in California, Oregon, and Nevada history, was caused by an atmospheric river storm.

The geological record shows that atmospheric river storms similar to the one that caused the Great Flood happen in California every 100-200 years.

If an atmospheric river storm "Big One" as modeled in the ARkStorm Scenario occurs, it would cause an estimated $725 billion to $1 trillion in damages and untold casualties.

Unfortunately, the likelihood of a massive flood caused by an atmospheric river storm is considered significantly higher now than in the past due to the effects of rising global average temperatures and climate change.

Source: (USGS)

How Are Atmospheric Rivers Measured?

Like rivers on land, atmospheric rivers are mostly beneficial or at least benign, except when they flood.

Like the tropical storm and hurricane scale, atmospheric rivers are categorized by extremity.

With tropical cyclones like hurricanes, the severity of the storm (and whether it gets a name) is determined by wind speed in miles per hour (Mph).

With atmospheric rivers, the metric is the volume of water vapor the system carries — which largely determines how beneficial or disastrous the potential rain or snowfall can be.

As you can see in the graphic above, precipitation from atmospheric rivers is often highly beneficial, particularly in states like California that frequently experience near-drought conditions.

More rain, in moderation, can also help prevent California wildfires like the ones that devastated so much of LA and SoCal early in 2025, or at least reduce how quickly and far they spread.

However, at Category 4, the risks outweigh the benefits and Category 5 can cause devastating mudslides and floods.

Final Thoughts

Like many naturally occurring weather phenomena, atmospheric rivers can have both a positive and a negative impact on human life, property, and the environment.

Extreme atmospheric river storms like the one in Los Angeles and SoCal in November 2025 carry substantial risks and can even lead to loss of life and destruction of property if flooding, mudslides, or other byproducts of heavy rainfall and storms occur.

Atmospheric rivers are not exotic events, unlike the recent sightings of the Northern Lights (Aurora Borealis) as far south as Florida caused by a rare category G4 geomagnetic solar storm.

Instead, these rivers in the sky are a natural, ever-present part of Earth's complex and interconnected climate and weather systems.

However, Category 4 and 5 atmospheric river storms can be potentially catastrophic events.

Inform yourself by checking for warnings from government agencies like the National Weather Service and always be prepared to be stuck indoors for several days or to evacuate, if it comes to that.

Stay safe.