Firefighters are working in extreme temperatures across the U.S. West and struggling to contain wildfires, the largest burning in California and Oregon, as another heat wave baked the region, straining power grids. The largest wildfire of the year in California is raging along the Nevada state line and has burned about 134 square miles. In Oregon, the Bootleg Fire exploded to 224 square miles as it raced through heavy timber in the Fremont-Winema National Forest. A wildfire in southeast Washington grew to almost 60 square miles while in Idaho, Gov. Brad Little has mobilized the National Guard to help fight fires sparked after lightning storms swept across the drought-stricken region.