PENTICTON, Aug. 10 -- The fire came so fast that some residents of Summerland, British Columbia, had only minutes to gather documents, photographs and medications before leaving homes their families had owned for generations. By the time the Bald Range wildfire crested the hills overlooking town, the road out was already clogged with cars and the air had turned a sickening orange-brown.

British Columbia declared a provincial state of emergency on Saturday as the Bald Range fire exploded from a few hundred hectares to roughly 50 square kilometres in a matter of hours, tearing through the Okanagan Valley with a ferocity officials said they had not witnessed before. More than 20,000 residents were ordered to evacuate, roughly 12,000 from Su...