A wildfire raging in California's Kings Canyon National Park forced the evacuation of about 20 homes and a heat wave prompted concern that the blaze will continue to spread, authorities said on Tuesday. At 98,000 acres (40,000 hectares), the so-called Rough Fire is the largest wildfire currently burning in California, the U.S. Forest Service said, as the state wilts under a heat wave expected to bring temperatures over 100 degrees Fahrenheit (37 Celsius).