(Reuters) - Hot, dry weather forecast for Thursday could stoke a fast-growing wildfire in central Arizona that firefighters are struggling to contain, authorities said.
The blaze, dubbed the Goodwin Fire, has charred 21,000 acres and destroyed a number of homes since starting on Saturday in the Prescott National Forest, 70 miles north of Phoenix.
Low humidity, temperatures hovering around 90 Fahrenheit and 35 mph (55 kph) wind gusts are in the forecast through the weekend and may "contribute to extreme fire behavior," the National Weather Service said in an advisory.
The National Forest Service said firefighters have carved containment lines around just 1 percent of the blaze's perimeter, and a Yavapai County spokesman said an estimated 3,000 homes and other buildings were under threat.
Residents from at least a dozen communities had been evacuated, he said.
The full extent of property losses has yet to be determined, said Tiffany Davila, a spokeswoman for the state Department of Forestry and Fire.
A force of about 1,000 fire personnel, backed by airplane tankers dumping payloads of flame-retardant chemicals, are trying to safeguard the most heavily populated areas on the northeastern fringe of the blaze, Davila said.
Governor Doug Ducey issued a state of emergency for Yavapai County, freeing up funds to help fight the blaze.
Heavy rainfall in parts of the West over the winter and spring helped delay the onset of wildfires, but it also spurred the growth of dense vegetation that has now dried out and is fueling fire activity as summertime heat sets in.
In Utah, another fierce wildfire has destroyed more than a dozen homes and forced the evacuation of 1,500 residents about 300 miles (483 km) south of Salt Lake City.
In California, several smaller wildfires burned, including a new blaze threatening hillside homes in the Los Angeles suburb of Burbank, and the so-called Hill Fire along the state's central coast.
(Reporting by Brendan O'Brien; Editing by Raissa Kasolowsky)