Atmospheric Rivers in BC, Mapped: Hope's 174 mm Day and Where the Big Storms Hit

On November 14, 2021, the weather station at Hope's airport recorded 174 mm of rain in a single day. Kamloops gets 247 mm in an average year. So Hope got about 71% of a Kamloops year in a single day, and another 103.5 mm the day after.

That was the atmospheric river that flooded the Fraser Valley. It's the biggest single day in the 25 BC stations I pulled from Environment Canada, going back to January 2014. This fall the south coast has started dry: from Oct 1 to 17, YVR logged 9.5 mm, about 18% of its 2014 to 2025 average for those dates. On September 21 the Province told communities to get ready for fall and winter flooding anyway, because, in its words, "a watershed can remain in drought and still experience flooding."

So here's where BC's big rain days actually land. There's a map with five layers, a checker that tells you how often it rains on any date (moving day, anyone?), a quiz, and what any of this means if you're buying a home.

What an atmospheric river is, in one paragraph

NOAA describes atmospheric rivers as long, narrow bands in the atmosphere, "like rivers in the sky," that carry most of the water vapour moving outside the tropics. When a strong one stalls against BC's mountains, the vapour comes down as rain or snow, and a lot of it. You've probably heard the Hawaii-flavoured version called the Pineapple Express. For this post I don't try to label each storm. I just count days: a soaker day is 25 mm or more of precipitation in one day, and the biggest days and three-day totals at each station are where the atmospheric rivers show up.

The map

Start with soaker days, then flip through the layers. The pattern is the same on every one: the outer coast and the mountain valleys right behind it get hammered, and the Interior barely notices. The Lower Mainland gets its own zoomed-in box, because Vancouver, West Vancouver, Squamish and Hope all sit within about 130 km of each other and get very different weather.

Who gets the most soaker days

Squamish wins, and it isn't close: 29.0 days a year with 25 mm or more, and 8.1 with 50 mm or more. That's ahead of Prince Rupert (21.9), which most people would have guessed. Prince Rupert gets rain more often (194 days a year with 1 mm or more, to Squamish's 141); Squamish gets it in bigger doses.

Then look at YVR and West Vancouver. The two stations are about 17 km apart. West Van's sits 170 m up the slope and averages 1,839 mm a year, 59% more than YVR's 1,159 mm, with 18.6 soaker days to YVR's 7.1. Same storms, one bridge, more mountain. Victoria has the fewest soakers of the nine south coast stations (4.5 a year). In the Okanagan they're close to a myth: Kelowna's station hasn't recorded a single 25 mm day since 2014 (its biggest was 22.7 mm), though about 11% of its days are missing.

The wettest day at each station

Each station's single biggest day since 2014, and its biggest three days in a row. Three stretches keep showing up: November 2021 (Hope, Abbotsford, Victoria, Nanaimo), October 19, 2024 (YVR and West Vancouver, which both had their wettest day in the whole period that day: 67.1 mm and 134.6 mm) and a run of storms in December 2025. The first of those gave Hope 134.2 mm on Dec 10; the Canadian Press reported the next day that floodwaters and landslides had cut most major routes between the Lower Mainland and the Interior, and that Abbotsford had ordered residents of 371 Sumas Prairie properties to evacuate. A second storm a few days later gave Squamish its wettest three days in the data, 232.7 mm from Dec 14.

In the Interior the biggest days tend to be summer ones. Prince George's top two days came in late July and early August, nowhere near storm season. Smithers is the odd one out: one 70.7 mm day in October 2017, and nothing else in the data over 39 mm.

November 2021, station by station

Here's the three-day total for Nov 13 to 15, 2021, at every station that reported all three days. Hope took 295 mm, Abbotsford 173 mm and West Vancouver 160 mm. Victoria got 154 mm, a big number for a city that averages 873 mm a year. The Canadian Press later summed up what followed: water from the Nooksack River inundated the Sumas Prairie, causing billions in damage. (Squamish, Sechelt, Terrace missed at least one of the three days, so they're left off.)

The north barely felt it. Port Hardy logged 13.9 mm over the same three days and Prince Rupert 23.6 mm. Atmospheric rivers are narrow. That's what makes them dangerous: all that water lands on a few valleys.

When storm season peaks

If you want a month to circle, it's November. YVR had 21 soaker days in November across 2014 to 2025, more than any other month, and 76% of all its soakers came between October and January. Across the nine south coast stations, that share is 69%. Summer soakers at YVR are rare: 1 in June, 0 in July and 3 in August over 12 years.

Hope's season starts early and runs late. It had 16 soaker days in September over the same years (YVR had 5) and 24 in February (YVR had 2). My read: if you're putting a Fraser Valley home on the market or booking a roof replacement, aim for May to August and assume September won't save you.

The all-at-once index

Here's a stat I made up: what share of a year's precipitation falls on its 10 wettest days? In Prince Rupert it's 22%, because it rains there all the time and no single day matters much. In Kamloops it's 41%. Kamloops is dry, until it isn't, and then 10 days deliver about two-fifths of the year. The Okanagan towns (Penticton, Kelowna) and Cranbrook are close behind.

Why care? A city's drainage, a strata's gutters and your basement don't see the yearly average. They see the worst few days. A low yearly total can still come with days that overwhelm a lot that was never graded for them.

This October so far: wet north, dry south

Storm season has started, just not everywhere. From Oct 1 to 17, 2026, Prince George got 66.9 mm, about 252% of its 2014 to 2025 average for those dates, and Prince Rupert 152.9 mm. Meanwhile YVR had 9.5 mm, Victoria 2.6 mm and Penticton 1.0 mm. These are preliminary numbers, a few stations are still missing a day or two, and some averages use fewer than 12 years because of gaps (Prince George's uses 8).

That fits the Province's September warning. Its release said drought persists across much of BC (Okanagan Lake was at its lowest level for the time of year in more than 80 years) and that longer dry periods can be followed by intense rainfall. It also warned that communities in and below burned areas may face higher risks of flooding, debris flows and landslides in heavy rain. My read: a dry October is no reason to put off cleaning the gutters.

A few answers from the checker. On July 1, Vancouver's moving day, YVR saw rain on 16% of days around that date. Halloween is a different story: 55% at YVR and 63% in Prince Rupert (for the trick-or-treat angle, see my Halloween rain and trick-or-treat map). If you're moving in mid-November, Kamloops (20%) is a far drier bet than Squamish (61%).

What it means if you're buying (or own)

Rain is part of the price of the coast, and the numbers above show it isn't spread evenly. On a 2,000 sq ft roof, YVR's yearly average works out to roughly 215,000 litres of water a year. Hope's 174 mm day would have put about 32,000 litres on that same roof in 24 hours. All of it needs somewhere to go.

West Vancouver's median asking price ($2.99M) is a lot higher than Vancouver's ($1.39M), so the extra rain obviously hasn't dragged asking prices down. These are asking prices of active listings on EstateBlock, not sale prices. For the North Shore market itself, see my North Vancouver real estate update.

Browse homes in Squamish, Abbotsford or West Vancouver on EstateBlock, or get an instant evaluation of your own place. For more weather data, see when it snows in Vancouver and 17 other Canadian cities.

How I did this

On 2026-10-18 I downloaded daily total precipitation (rain plus melted snow, in mm) for 25 BC weather stations from Environment and Climate Change Canada's climate-daily API, from Jan 1, 2014 to Oct 17, 2026. Many are airport stations; tap a station on the map for its name and elevation. A station is a point, so a town's other neighbourhoods can get more or less. West Vancouver's station, for example, is 170 m up the hill. Where an airport switched to a new station ID at the same site (Hope, Port Hardy), I used the second ID only on days the first had no value.

Yearly figures (rain per year, soaker days, the all-at-once index, the moving-day checker) use calendar years 2014 to 2025 and only days with data, scaled to a 365.25-day year. Every station reported more than 80% of days; Bella Coola's record starts in late 2015 and is the thinnest at 82%. Missing days can hide a big storm, which is why a few stations show "no data" for November 2021. The October 2026 figures are preliminary and compare with the 2014 to 2025 average for the same dates (not ECCC's official climate normals), using only years with all those dates reported. I don't classify individual storms as atmospheric rivers; the definition comes from NOAA, and the counts are just heavy-rain days. The jokes are about weather and towns. Nobody who lived through the 2021 or 2025 floods is the punchline.

Contains information licensed under the Open Government Licence – Canada.