It’s Armel Castellan’s job to know the weather 24/7. As Environment and Climate Change Canada’s disaster preparedness meteorologist for B.C. and Yukon, he’s constantly on the lookout for extremes: subtropical cyclones, arctic cold fronts, floods, heat waves and fire weather.

When he looked at the weather models in mid-June of 2021, he felt his heart beating in his throat. The skull-crushing ridge of high pressure he saw headed toward B.C. was so powerful, he knew immediately it would blanket a vast area in deadly heat. The models were forecasting temperatures so far outside of normal that the map interface on Castellan’s computer was displaying all new colours—greys and whites on a spectrum of intensity he’d only ever seen go to dark red. Within days, European, American and Japanese weather models converged on a consensus: a record-breaking pressure cooker would soon envelop western North America.

“We knew records were going to be broken,” says Castellan. “But that doesn’t give you the reality of what was about to happen.” Temperature records typically break by tenths of degrees, like speed records for the 100-metre dash. At its apex, the heat dome that engulfed B.C. that month eclipsed some records by more than five degrees, driving temperatures up to 25 degrees C beyond seasonal averages.

Across the region, roads buckled, car windows cracked and power cables melted. The emerald fringes of conifers browned overnight, as if singed by flame. Entire cherry orchards were destroyed, the fruit stewed on the trees. More than 650,000 farm animals died of heat stress. Hundreds of thousands of honeybees perished, their organs exploding outside their bodies. Billions of shoreline creatures, especially shellfish, simply baked to death, strewing beaches with empty shells and a fetid stench that lingered for weeks. Birds and insects went unnervingly silent. All the while the skies were hazy but clear, the air preternaturally still, not a cloud in sight. The air pressure was so high they’d all dissipated.

Then came the fires. For three days in a row, the village of Lytton sustained temperatures more typical of the Sahara Desert or Death Valley, setting new Canadian records each day, before peaking at 49.6 degrees C [122 Fahrenheit]. On the fourth day, the village burned to the ground. The day of the inferno, the B.C. Wildfire Service’s Fire Weather Index, which usually tops out at around 30, hit 132. In the days that followed, smoke-fed thunderclouds formed over two conflagrations, generating 121,000 lightning strikes in a single evening, igniting more fires.

Air pollution levels in some communities reached more than 40 times the safe limit.

That week, the province recorded the largest number of ambulance dispatches ever. Kyle Merritt, an emergency doctor at Kootenay Lake Hospital in Nelson, saw a wide range of cascading health effects: heat exhaustion, of course, but also acute psychological crises, including suicidal ideation and panic attacks. Something about breathing that noxious air for so many days on end was deeply destabilizing.

On the chart of one patient suffering from heatstroke, he wrote “climate change” as the underlying cause—as far as he knows, a world first. Others developed respiratory problems that, even after the fires abated, never went away. All told, the heat dome directly killed more than 600 British Columbians, making it the deadliest weather event in Canadian history. Mortality rates among the elderly remained elevated for months afterwards.

As the heat crescendo-ed at the end of June, Castellan’s days were packed with dozens of media interviews from his home office in Victoria, which was unwisely located in the hottest part of his house. He hydrated between speaking to the New York Times and Reuters. At night, he set up a tent in his backyard so his three young children’s bodies could cool down. When Victoria set a record high of 39.8 degrees [104 F], he tried not to think too hard about what that meant for the future his kids would inherit.

“There’s an apocalyptic feel to something that different,” says Castellan. “It’s like when you witness an eclipse. There’s that very strange sensation: all of a sudden it gets dark in the middle of the day, and the birds go quiet, and everything is strange. It was like that, on a multi-day level. It’s like the sun just grew in size.”