Troutdale, Oregon

SOME fires suddenly exploded in size. One in Montana doubled in 24 hours, charring 78 square miles overnight - an area bigger than Brooklyn, a borough in New York City. Already-burning fires started new ones, shooting embers like artillery barrages, including one that apparently jumped several miles across the Columbia River into Washington from Oregon, breaching a natural firebreak that long seemed impregnable.

Extreme fire behaviour - difficult to predict and dangerous to fight - has been the watchword of the 2017 season across the US West. More large, uncontrolled wildfires were burning in 10 Western states in early September than at any comparable time since 2006.