The brush fires that swept across San Diego County on Wednesday were fueled by a dangerous mix of record-high temperatures and strong winds that officials say are unusual for May.
The fires were more proof that California's drought conditions have created a year-round fire season.
"In San Diego County, what we're experiencing over the last several days is high temperatures, low humidity and very high winds. That's a weather pattern that we usually see in the fall," said Cal Fire spokesman Daniel Berlant. "All it took was the spark of a fire."
Temperatures at Lindbergh Field in San Diego were at a record-breaking high of 93 degrees, possibly higher, by Wednesday afternoon, said National Weather Service meteorologist Mark Moede. The former record on this day was 87 degrees in 1956, and the typical temperature is 68 degrees, Moede said.
In Orange County, temperatures at John Wayne Airport hit 105 degrees Wedneday. The average high temperature for this day is 72 degrees. Relative humidity was at 3%, which Moede said was also a surprise.
"This is very unusual for the middle of May in Santa Ana," Moede said. "Usually we have a marine layer, the typical May gray."
Officials had this weather forecast about a week in advance. Over the weekend, Cal Fire had begun increasing equipment and staffing from the Central Valley down to Southern California in preparation for potential fires this week, Berlant said.
In just the period between January and mid-May this year, Cal Fire has already fought about 1,400 wildfires across the state -- more than twice the average number for this time of year, Berlant said.
"It starts with the drought," Berlant said. "The grass, the brush and the trees -- not only in San Diego County, really across California -- are really dry."
The drought and increase in fires prompted Cal Fire to keep the same number of firefighters, helicopters and equipment in Southern California usually reserved for fire season in the fall. "Fire season from 2013 rolled right into 2014 and continues with no end in sight," Berlant said.
Weather officials are expecting even hotter weather Thursday. In Los Angeles county, temperatures at Lancaster Airport and Palmdale Airport could be higher than their 99-degree daily records set in 2013 and 1996 respectively, according to the National Weather Service in Oxnard.
In San Diego, winds won't be quite as strong on Thursday, but temperatures will be even higher, Moede said.
There is cool relief in sight, if only temporarily.
"Over the weekend, we're going to start seeing a dramatic cooling trend," Moede said. "By early next week, we'll start seeing what's normal temperature-wise. Highs in the 60s and low 70s in the coastal zones."