FIREFIGHTERS battling wildfires in California caught a break as gusty winds died down, but with the region bracing for sweltering heat the respite could be brief, authorities said.

A four-day-old fire in California coastal canyons was 45 per cent contained after 40mph "sundowner" winds failed to materialise.

Those gusts had driven the flames through steep, brushy canyons west of Santa Barbara on previous nights and forced the closure of a major highway.

No homes have burned, but about 270 homes and ranches are at risk and camp sites were evacuated with flames only two miles from more densely populated coastal communities.

In New Mexico, governor Susana Martinez directed the state National Guard to assist in securing communities affected by a massive wildfire in the central part of the state. Guardsmen will be patrolling and protecting evacuated homes from possible looting. They also will be called on to help with potential flooding.

Firefighters took advantage of cooler weather to reinforce holding lines around a blaze that has destroyed two dozen homes. Fire lines were strengthened on the western and southern boundaries of a blaze that erupted in the Manzano Mountains south of Albuquerque.

The fire has burned more than 27 square miles about six miles north west of Tajique since Tuesday and spread a pall of smoke as far as Denver. The damage includes 24 homes and nearly as many structures near the small community of Chilili.

In Arizona, a fire south west of Show Low was 30 per cent contained. Firefighters beefed up containment areas on the northern and western sides of the blaze.

Evacuation orders remain in effect for the community of Forestdale. The fire has burned nearly 19 square miles since Wednesday.

Crews in Utah also made gains against three wildfires in the southern part of the state.

A 350-acre wildfire near Cedar City was 30% contained, but the blaze still threatened 20 structures including homes and outbuildings.

More than 1,200 firefighters attacked the California fire, which has engulfed nearly 12 square miles of mountain and agricultural lands. Crews nailed down lines on the fire's west side, which had not moved for days, Santa Barbara County fire chief Dave Zaniboni said.

However, the eastern side of the blaze was uncontrolled and virtually inaccessible.

"It's straight up and down... we can't put bulldozers in there," Zaniboni said.

Crews were relying on aircraft water drops and on cutting fire breaks ahead of the flames. They hoped to set backfires to stop the spread, Zaniboni said.

The battle had a deadline because "sundowner" winds gusting to 50mph are expected to return and that could stir up the fire, he added.

Weekend fire dangers were already expected to worsen as a heatwave will bring potentially record-breaking temperatures across the south west.