More than 200 firefighters are battling a wildfire north-east of Phoenix in Arizona that threatens scores of homes and has forced dozens of residents to evacuate.

No structures have been damaged as the wildfire traversed nearly six square miles on the cusp of the Boulder Heights subdivision, officials said.

There were 275 people combating the fire on Saturday as temperatures surpassed 38C before midday, with wind gusts expected in the afternoon.

“We still have unseasonably high humidity, hot weather,” a fire official said.

“We have no wind right now, but gusts were predicted.”

Air tankers and helicopters have helped douse flames from the sky above the Boulder View Fire. The cause of the fire is under investigation.

It began about five miles east of Carefree, just outside northern Scottsdale on the edge of the Tonto National Forest.

The Red Cross has set up an evacuation centre at a high school in Scottsdale, and shelters for horses and other large animals were established at several locations, including the rodeo grounds at nearby Cave Creek.

In central California, increasing temperatures and low relative humidity this weekend could result in worsening wildfire conditions for the Fresno June Lightning Complex.

The complex – made up of three large fires in eastern Fresno County as well as several smaller fires – took up nearly 17 square miles and was estimated to be 42% contained by Saturday morning. One structure was confirmed destroyed, and evacuation orders remained in place.