Yosemite Fire Threatens Homes, Drinking Water

30 mph winds have caused a phenomenon known as "crowning."
1:53 | 08/26/13

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Transcript for Yosemite Fire Threatens Homes, Drinking Water
wildfire raging out west in california. Take a look at these arresting pictures of the inferno around yosemite right now. Abc's neal karlinsky is on the fire line with all the latest. Neal. Reporter: George, good morning. The fire remains stuck, it seems, in a frustrating and very dangerous pattern. It is still only about 7% contained. It continues to burn very, very hot. What they need here is a break in the weather. It is a fire that poses every threat imaginable. TEMPERATURES IN THE 90s MIXED With bone-dry trees in the midst of a drought. Steep, rugged terrain and then this. The winds gusting to 30 miles an hour created a phenomenon known as crowning where the tops of tree torch. Fire that skips along spreading faster than on the ground. All that intensity is creating its own weather pattern big enough to be seen from space. Something called thunderous pyrocumulus clouds that can alter the wind direction rapidly and potentially trap firefighters. We are expecting the wind to push tonight, whether it comes or not we don't know but planning on that. Reporter: The fire has taken on a life of its own and is now essentially the size of chicago. But it's yosemite, an american treasure, that's the priority. Teams are protecting three dozen of the park's famous sequoia trees among the oldest living things on earth. Other teams are working to protect the massive hetch hetchy reservoir inside yosemite that supplies 85% of san francisco's water. Enough of a threat for california's governor to declare a state of emergency, worried san francisco's water will be polluted with ash. So hard for life to go on as normal here. Kids were supposed to go back to school last week. They still haven't and won't again today because of all the smoke.

This transcript has been automatically generated and may not be 100% accurate.

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