After a week of lightning-sparked blazes, more than 160 square miles of Nevada rangeland was burning or blackened Friday — the most land scorched by wildfires in the country this year, a national fire center said.

Four of the more than dozen fires in the state accounted for most of the area burned, according to the National Fire Information Center in Boise, Idaho. One fire covers about 75 square miles near the Big Rocks Wilderness.

Oregon had the nation's second largest amount of land charred by wildfires, with 123 square miles were ablaze Friday or already burned, the fire center said.

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The magnitude of the nation's wildfires has forced firefighters to adjust their tactics.

"Because of the large number of fires going on in the West, we cannot get requested aviation or other resources quickly, which could be used for a direct attack," Bureau of Land Management Field Manager Helen Hankins said in Elko, Nev.

Firefighters in Oregon battled a blaze Friday that prompted evacuation orders for about 500 residents near the tourist town of Sisters in the central part of the state.

Firefighters also raced to beat high winds predicted Saturday that could drive a fire near the Oregon border into the major transmission lines that carry power between California and the Pacific Northwest.

The fire, about 70 miles northwest of Redding in the Shasta-Trinity National Forest, is burning between three transmission lines located about 1 1/2 miles apart.

Firefighters working through the night Thursday took advantage of cool temperatures and calm winds to contain half the fire in the remote area, officials said.

The California Independent System Operator, which manages the state's power grid, has contingency plans to reroute electricity around the transmission lines if one or more fail or have to be shut down because of the fire, said Jim Detmers, the system's vice president for operations.

In South Dakota, firefighters battling 106-degree temperatures made some progress fighting a wind-blown wildfire near Rapid City as they waited for reinforcements and more equipment.

The fire has destroyed at least one home and prompted evacuation orders for about 300 homes in the potential fire path, officials said.

The blaze has burned about 4 1/2 square miles and was about 10 percent contained, authorities said.

"We've have some of the worst fire conditions in history in western South Dakota," Gov. Mike Rounds said Friday after touring the fire sites a day earlier.

In Nebraska, the National Guard has been called to help fight five wildfires in the northwest corner of the state's panhandle.

Firefighters estimated that one of the fires has blackened between 9 and 16 square miles.

Some homes have been evacuated in Banner County, and additional evacuations are being evaluated, Gov. Dave Heineman's office said.

Wyoming firefighters battled a new wind-whipped wildfire in Platte County with no help from federal crews who are busy with fires elsewhere, an official said.

Assistant State Forester Ray Weidenhaft said the flames were so intense and moving so quickly that firefighters were unable to get an accurate reading of its size.

By the latest estimate, the fire had burned more than 9 square miles, he said. It was burning north of Hartville, a community of about 75 residents in eastern Wyoming.