Rain and chilly weather are slowing the spread of fires in Southern California. Wildfires ranging from north of Los Angeles to the Mexican border have killed at least 20 people and destroyed 2,800 houses. But the weather is also posing new problems for firefighters.

The headline in a San Bernardino newspaper said Rain to the Rescue, as temperatures in nearby mountain resorts dipped overnight to the freezing point.

According to fire chief Ron Collier, the cooler weather, combined with rain and fog, have helped the firefighters, but he says it also causes them some problems.

"But it's also hard on the firefighters because the coldness, once they get wet, then hypothermia sets in and it's difficult," he said. "And so we have to watch their work periods. We have to give them coffee to make sure that they keep a little bit warm. So it adds another element to firefighting that these folks are very capable of doing."

Volunteers in San Bernardino are ferrying warm clothes and supplies to those on the fire lines. Local resident Ron Miltier said firefighters saved his house, and so he's helping.

"They're doing a great job. They're all so young," he said. "You wouldn't believe that these guys can even do this job, but they do an excellent job. So we're just letting them know that we really appreciate them."

The mountain town of Big Bear Lake is still under threat from the flames. Fifteen-thousand people remain evacuated from the region, and this firefighter said he and his colleagues are preparing for the worst. He explained, "What we're out here doing is basically trying to prep the structures for the approach of the fire, doing the things that we can to make these houses defensible, pulling flammables away from the house, clearing around the propane tanks, cutting down limbs that are over the roof line or in the power lines."

Firefighters say a nearby area full of dead pine and fir trees is a potential hazard. They call it a "sleeping giant" should the flames reach it.

The news is better near Simi Valley, north of Los Angeles, where a major fire is nearly 50 percent contained. Resident Jim Mitchell said his home and business are out of danger.

"I'm very thankful. I'm glad it's over and I'm looking forward to never having to experience anything like this again," he said.

Seven fires are still burning in four California counties. Officials say that, if the weather holds, all of the blazes may be under control within a week or so. But if hot desert winds pick up again, containment will take longer.