On Monday, every Metro Vancouver air quality station that measures fine particulate matter —from Horseshoe Bay to Hope — registered levels well above the regional district’s air quality objective, prompting continued health warnings. There are two ways smoke from the hundreds of wildfires burning in B.C.’s interior and northern regions travels through the province’s mountainous landscape and into the Lower Mainland airshed.

In some cases, there’s so much smoke it blows up and over the mountain tops. But a lot of it pours through the valleys between mountains, covering communities at the narrow end of the Lower Fraser Valley like Hope and Agassiz with a concentrated cloud of smoke.

There are “some satellite pictures where you can see all the mountain tops, but then all the valleys are obscured in smoke,” said Francis Reis, a senior project engineer in Metro Vancouver’s air quality and climate change division. In some ways, the air quality monitors in Hope and Agassiz are an early warning system for pollutants travelling through the Fraser River and Harrison Lake valleys from the interior, Reis said.

“Because it’s a little narrow V-shaped valley, the smoke is likely to be more concentrated, the air hasn’t had a chance to spread out and mix with less polluted air,” he said. “I think that’s why we saw really high values at Hope over the weekend; Hope just basically got a really concentrated cloud of smoke coming from one of the northern fire.”

While the air quality is highly variable as the smokiness shifts with the wind, in the late morning hours Monday some of the worst fine particulate readings were in the eastern, narrower parts of the valley.

In Hope, there were 140.1 micrograms/m3 of fine particulates as of 11 a.m., close to six times the air quality objective of 25 micrograms/m3 per 24 hours. In Agassiz, there were 110.4 micrograms/m3 and in Chilliwack, it was 68 micrograms/m3.

Jna Winterhoff, a mother of six children, said for her Chilliwack family the smoke has meant a lot of time indoors. “It’s definitely limited what we’re able to do or what I feel comfortable bringing the kids to do — band a lot of that is because of Paul,” she said.

Paul, who is 18 months old, was born with aortic valve stenosis, which means his heart’s aortic valve is narrower than it should be, his mom explained over the phone from the hospital where her son is set to have surgery next week. The smoke in the air is an added stress on his body, she said. “It gets in the lungs and it makes it harder to breath, which in turn can up your heart rate.”

“Some days you open the window and you can smell the smoke, and so we’ve kind of holed up in the house,” Winterhoff said. But even inside, Paul’s throat has been irritated.

“It’s definitely limited what we can do. We probably would have gone to the water park a few more times or gone to the lake, or even just the kids playing outside on their bikes. They haven’t really been doing too much of that,” she said. “I’m ready for rain. It’s unfortunate, it’s everywhere. I don’t remember this happening when we were kids.”

As the climate continues to change, B.C. is bracing for more severe wildfire seasons, which means days or weeks of poor air quality could become the norm.

When it comes to health impacts, the most significant concerns are for pregnant women, particularly if there are already concerns about the pregnancy; very young children and people with pre-existing heart and lung diseases, said Dr. Michael Brauer, a UBC professor at the school of population and public health.

For young children with any kind of respiratory infection, the poor air quality could make it harder for them to fight the infection, raising the possibility that it could develop into something more severe, like pneumonia, Brauer said. For people with pre-existing conditions like heart disease or chronic lung diseases, Brauer said it could make it very difficult to breathe or even trigger heart attacks or strokes.