Firefighters wary of hot winds fanning San Diego-area wildfire

A helicopter drops water near the Rancho Santa Fe neighborhood of San Diego on Tuesday, May 13. A wildfire forced the evacuation of more than 20,000 homes in Southern California, officials said, as a high-pressure system brought unseasonable heat and gusty winds to the parched state.

(CNN) -- Hundreds of firefighters were battling Wednesday to contain a San Diego wildfire, concerned that California's so-called devil winds would ignite flareups, authorities said.

Authorities were concerned that hot, dry gusts called Santa Ana winds would set back their efforts since Tuesday morning to contain the wildfire, which improved overnight to 25% from 5%, said Cal Fire incident commander Ray Chaney.

The fire has burned 1,584 acres and prompted an evacuation Tuesday of 5,000 homes in San Diego and selected areas, authorities said. By Tuesday night, those residents had an "orderly return" to their homes, San Diego Police Chief Shelley Zimmerman said.

As of Wednesday morning, no structures were damaged, and only two minor injuries -- for smoke exposure and heat-related illness -- were reported, Chaney said.

In addition to the Santa Ana winds, 350 firefighters were expecting single-digit humidity, Chaney said.

"It does put us on edge," Chaney said of the forecast. "The weather is a very big concern for us."

Added Rancho Santa Fe Fire Department Chief Tony Michel: "The winds are going to be a problem."

"The battle isn't over," said San Diego Mayor Kevin L. Faulconer. "We have had crews out there that have worked all night."

The cause of the blaze, called the Bernardo Fire, is still under investigation, he said.

At one point Tuesday, parents were told to pick up their children from three elementary schools because of the fire.

"It has been, to say the least, a very challenging day for local fire agencies and law enforcement agencies," San Diego Fire Chief Javier Mainar said. "It is unusual in May to have wind-driven fires like this that prove to be such a challenge to contain."

Michel agreed, saying there's a long, hot summer ahead. "This is going to be a pretty severe fire season," he said. "We're in a prolonged drought."

The National Weather Service issued a red flag warning for areas around San Diego through 8 p.m. Wednesday. As the agency noted, "a red flag warning means that critical fire weather conditions are either occurring now or will shortly," with strong winds, low humidity and warm temperatures feeding into "extreme fire behavior."