About 100 Yosemite National Park visitors were evacuated by helicopter yesterday when a wildfire that started weeks ago in the park's backcountry grew unexpectedly to at least 700 acres, officials say. Some of the evacuees included hikers who had climbed the park's iconic Half Dome peak, rising nearly 5,000 feet above Yosemite Valley, while others had to be airlifted from campgrounds and hiking trails in the area, a park spokeswoman says. Firefighters had monitored and controlled the lightning-sparked fire that started several weeks ago, the spokeswoman says, but strong winds and high temperatures ignited a spot fire yesterday and it rapidly grew. (More Yosemite National Park stories.)