About 170 firefighters are battling hot weather and dry conditions in a rugged part of northern Nevada's Stillwater Mountains where a lightning-sparked wildfire has nearly doubled in size but is threatening no structures about 100 miles (160 kilometers) east of Reno. Temperatures climbed into the high 90s Wednesday in the area northeast of Fallon and the Stillwater National Wildlife Refuge about 75 miles (120 kilometers) south of Winnemucca. The Bureau of Land Management says two air tankers and four helicopters assisted ground crews that dug a line around about 5% of the fire that's burned more than 3.5 square miles (9 sq. kilometers) since it broke out Tuesday afternoon. They hope to achieve 25% containment by Thursday. In addition to dropping water on the flames, helicopters are shuttling crews into remote areas difficult to access.