Unusual atmospheric river will impact B.C. for days, even after it ends, says expert

As heavy rain continues to drench the Lower Mainland, the potential for flooding is a growing concern.

The current atmospheric river drenching British Columbia is unusual, for both its duration and timing, says an Environment Canada meteorologist, and its effects will last for days, even after it ends.

“We typically don’t seem to get atmospheric rivers this time of year that are quite this strong,” Brian Proctor says in an interview.

While storms in March are not unusual, per se, it is unusual to see storms with so much rain last so long, he adds.

The Pacific region around Hawaii is the source of the rain, he says.

“So, the warmer an air mass is, the more moisture it can carry, and when you get an atmospheric river, you basically start directing it like a fire hose onto certain portions of the coast.”

What is unusual about this storm is its length of intense rainfalls, he adds.

While this phenomenon will require additional study, it is “largely due to a really, really strong ridge of high pressure that is centred off California that hasn’t moved,” he says.

Proctor says this ridge has not only brought unusually high temperatures to California and Arizona for this time of the year, but also funnelled the atmospheric river onto B.C.’s coastlines.

“It’s allowed the atmospheric river to ride along the northern edge of that ridge of high pressure,” he says.

Proctor says the system causing the atmospheric river will have ended by Friday morning, but its conclusion will merely be the prelude for more weather-related developments.

Proctor says B.C. will need a prolonged period of dry weather for things to settle down.

“It’s going to take us days to recover from this precipitation in some of these drainage basins,” he says, adding that they are beyond their capacity to run off the moisture.

British Columbians can expect “far more seasonal light temperatures” but also “probably a lot of gusty southwest winds in many communities,” he says.

These winds, he says, could knock down a lot of trees, whose roots will already be saturated.

Areas that could be hit the hardest by these winds include portions of Vancouver Island, Vancouver, the lower Fraser River Valley, followed by the Interior parts of the province, he says.

Proctor also points to the possibility of mud and landslides, especially in areas that already have had a history of such events.

Soils saturated by days of rain are already starting to slip.

BC Hydro says a rock or mudslide knocked down a power line in the Metro Vancouver community of Coquitlam, B.C., early Thursday, temporarily leaving some 5,000 people without power.

Other British Columbians are also anxious about the stability of nearby slopes, including residents living in parts of the Central Coast Regional District along B.C.’s central coast.

Officials in that area have expanded a local state of emergency and evacuation orders because of flooding and the risk of landslides.

The district says the local state of emergency now covers the entire area that includes Ocean Falls, B.C.

The district said late Wednesday that it had also placed parts of the community under an evacuation order after an aerial assessment of local slopes.

While nobody resides in the newly declared evacuation zone, the district says the order is a precautionary measure to save lives, as the landslide is hazard is very high.

It says that the new order builds on an existing one for the eastern section of Martin Valley near Ocean Falls.

Authorities say that order remains in effect, as does the evacuation alert for the western section of Martin Valley.

The atmospheric river soaking the province’s coastal regions has also brought unseasonable warmth, breaking century-old daily temperature records in several Interior communities.

Environment Canada said seven communities reported record high daily temperatures Wednesday.

Those include Kamloops, where the temperature reached 21.8 C, breaking the record set in 1910, as well as in Quesnel and Salmon Arm, where records set in 1901 and 1915 were broken.

Salmon Arm’s high temperature reached 21.7 C, shattering the old mark of 16.7 C.

Rainfall warnings are also in place on western Vancouver Island, the Fraser Valley, Howe Sound, Sea to Sky and parts of the Metro Vancouver regions.

The forecast calls for up to 130 millimetres of rain to fall before Friday, with some places already reporting in excess of 200 millimetres since the atmospheric river event made landfall Sunday.

Proctor says the atmospheric river has significantly raised freezing levels.

“We really decimated the snowpack on Vancouver Island, and some of the coastal mountains,” he says. This means less water will be available in the spring, he adds.

“So, that’s always, always a concern from an agricultural, from an industrial, even from a residential point of view, as well as a fire weather point of view,” he says.

More immediately, the higher temperature raises the risk of avalanches in B.C.’s Rockies, he adds.

This report by The Canadian Press was first published March 19, 2026.