BOISE, Idaho - Wildfires across the country have scorched more land in 2006 than in any year since at least 1960, burning an area twice the size of New Jersey.

But the flames have mainly raced across sparsely populated desert, causing fewer firefighter deaths than in previous years.

As of Wednesday, blazes had torched 8.69 million acres, or 13,584 square miles, just above last year's total of 13,573 square miles, according to the National Interagency Fire Center in Boise. Reliable records were not kept before 1960, officials said. The annual average over the past 10 years is 4.9 million acres.

Federal officials attributed the increase to two consecutive seasons of hot and dry weather that left forest and ranges parched and easily ignited by lightning.

Fifteen federal, state and local firefighters have died this year battling wildland fires, the center reported. The worst single accident this year was a helicopter crash Aug. 13 in Idaho that killed three firefighters and the pilot.

Rose Davis of the NIFC said the 2006 acreage was skewed by unusually large early season range fires in Texas and Oklahoma - blazes that burned mainly sparsely populated areas and did not lead to large numbers of deaths or heavy damage to homes.

The Interior Department and the U.S. Forest Service have spent about $1.25 billion fighting the fires since the fiscal 2006 year began last Oct. 1.

The wildfire season may almost be over. Cooler weather and upper-elevation snow are expected in the Northwest.