© Reuters/Rick Wilking
A deadly, stubborn wildfire that ranks as the most destructive on record for Colorado has scorched more than 100 square miles (259 square km) of rugged mountain terrain northwest of Denver, but a cool snap on Wednesday gave fire crews a chance to take the offensive.

The so-called High Park Fire already is blamed for one death and has consumed 189 homes in the 12 days since it was ignited by lightning at the edge of the Roosevelt National Forest, and authorities say they expect property losses to climb once more damage assessments are made.

As of Wednesday, an estimated 1,000 homes remained evacuated on the western outskirts of Fort Collins, a city of more 140,000 people that lies adjacent to the national forest about 55 miles north of Denver, according to Larimer County Sheriff's spokesman John Schulz.

The only casualty reported from the fire so far was a 62-year-old grandmother whose body was found last week in the ashes of a cabin where she lived alone. She was the fourth person to die in a Colorado wildfire this year.

The High Park blaze grew in size by several thousand acres overnight and early Wednesday, extending to almost 66,000 acres, or nearly 103 square miles (266 square km).

But with air temperatures falling and expected to remain relatively cool for the next two days, fire managers plan to go on the attack.

"Today we're going to be aggressive," incident commander Bill Hahnenberg said. So far, a contingent of several hundred firefighters had managed to carve containment lines around 55 percent of the fire's perimeter.

The blaze was one of the biggest - and most threatening - of 16 large wildfires being fought across the country on Wednesday. Most were in seven Western states - Colorado, Wyoming, Nevada, New Mexico, Arizona, California and Utah, the National Interagency Fire Center in Boise, Idaho, reported.

Although federal authorities say the fire season has gotten off to an early start this summer in parts of the Northern Rockies, the number of fires and acreage burned nationwide is still well below the 10-year average for this time of year, according to fire agency records.

In a reminder that even relatively small fires can cause significant upheaval, a 450-acre (182-hectare) blaze burning near the town of Lake Isabella, nestled within the Sequoia National Forest in California, prompted the evacuation of about 160 homes and cabins, as well as the Hungry Gulch campground near Sequoia National Park.

But Forest Service officials say that blaze is more than 35 percent contained and no structures have been damaged.

An even smaller was reported on Tuesday to have destroyed six houses and five outbuildings near Mountain Home, Idaho, some 40 miles southeast of Boise.