(NBC News) Nearly 4,000 firefighters are battling the massive "Rim Fire" burning along the edge of Yosemite National Park, almost one for each of the homes still threatened by the flames.
Evacuees and those living nearby are on edge.
Strike teams continue to push back, digging out containment lines, holding off the flames and making progress.
Containment has climbed to 20 percent, but there's barely time to take a breath.
Working around the clock, crews know they can't slow down or take a break because the fire won't do the same.
Overwhelming conditions, even for veteran firefighters.
"I've fought fire from Alaska to Florida, from New England to California and this is one of the toughest fights I've ever faced," says fire chief Chris Schow.
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