A Death Valley hiker gave an interview as temps soared to 121°F. Hours later, he died.

Over the roughly 10 years he’s lived in Tumbler Ridge, Curtis Miedzinski almost never heard noises that disrupted the sleepy mountain town’s tranquil quiet. That changed late Tuesday afternoon, when the distinct thump of helicopter blades cut through the silence. With a population just under 2,400, Tumbler Ridge is tucked away in the dense forests of the British Columbia interior, and is surrounded by three mountain ridges that give the municipality a distinct feeling of remoteness, residents say. That seclusion seemingly complicated emergency services’ efforts to respond to a mass...