ALBUQUERQUE, N.M. (AP) – Firefighters were expected to work against extreme heat and gusty winds Wednesday as they battle a wildfire that has consumed thousands of acres of pinon and juniper forest along with grazing lands that Navajo Nation livestock owners have used for centuries.

The Assayii Lake Fire has charred more than 20 square miles near the Arizona-New Mexico border and destroyed a handful of structures, fire officials said. Fifty homes near the Native American communities of Naschitti and Sheep Spring were threatened, with some in Naschitti evacuated.

Depending on the weather, crews planned to construct fire line on the west and east sides of the fire and protect a communication tower to the north. The unfavorable weather has hampered efforts to directly attack the flames.

The blaze started June 13 and was making its way across traditional summer and winter grazing areas in the Chuska Mountains. Authorities urged some Navajo families to refrain from heading into the mountains in search of their sheep and other livestock.

“They really do value the life of their livestock more than they value their own,” fire spokeswoman Shari Malone said. “It’s been difficult.”

Sheep are a staple of life for the Navajo, who use their wool for rugs and mutton for meals at home and in restaurants.

The tribe withstood the federal government’s scorched-earth campaign during the 1860s in which their orchards and herds were destroyed in an effort to force them from their homeland. Decades later, they were forced to recover again after the government downsized their herds.

The Navajo Department of Agriculture was busy rounding up trailers to move some of the livestock brought down from the mountain before the fire made its run Monday. Some tribal members took to social media to ask for hay and water donations.

More than 680 firefighters and other personnel are assigned to the blaze, along with dozens of engines, helicopters and planes.

Elsewhere, diminishing winds have helped firefighters nearly contain a blaze burning near Lake Isabella in California’s southern Sierra Nevada. The blaze was 90 percent contained Wednesday morning with no flames jumping the perimeter.

In northern Arizona, a 12-acre wildfire that broke out in Oak Creek Canyon was 25 percent contained. The fire was just north of a blaze that charred 31 square miles last month in the scenic canyon between Sedona and Flagstaff.