>>> A FAST GROWING WILDFIRE IN SOUTHERN CALIFORNIA HAS QUADRUPLED IN SIZE. THE LINE FIRE IS BURNING OUT OF CONTROL IN THE SAN BERNANDINO MOUNTAINS EAST OF LOS ANGELES. THOUSANDS HAVE FLED THEIR HOMES, AS FIREFIGHTERS BATTLE NOT JUST THE FLAMES, BUT ALSO THOSE TRIPLE DIGIT HEAT -- OR TEMPERATURES THAT THEY'RE FACING. CALIFORNIA'S GOVERNOR HAS DECLARED A STATE OF EMERGENCY. SO OUR BEN TRACY IS IN MENTONE, CALIFORNIA. BEN, GOOD MORNING. >> Reporter: GOOD MORNING, ANNE- MARIE. SO FIREFIGHTERS HAVE BEEN BATTLING THIS THING ALL NIGHT LONG HERE IN THE SAN BERNANDINO NATIONAL FOREST. AS YOU CAN SEE BEHIND ME, IT'S VERY STEEP TERRAIN. THAT HAS MADE THIS A REAL CHALLENGE FOR FIREFIGHTERS. THERE ARE MORE THAN 36,000 STRUCTURES THAT ARE THREATENED BY THIS FIRE, AND AS OF NOW, IT IS STILL ZERO PERCENT CONTAINED. THE LINE FIRE OUTSIDE OF LOS ANGELES EXPLODED OVER THE WEEKEND IN THE SAN BERNANDINO NATIONAL FOREST, AND IS BURNING OUT OF CONTROL. >> THERE'S A LOT OF MOVING PARTS THAT ARE GOING ON WITH THIS FIRE RIGHT NOW. >> Reporter: MORE THAN 600 FIREFIGHTERS ARE TRYING TO SLOW THE SPREAD OF THE BLAZE, WHICH IS SO INTENSE IT'S CREATED ITS OWN WEATHER SYSTEM. >> THUNDER HEADS ACCUMULATING, WHICH CAN CREATE SOME OUTFLOW WINDS, WHICH CAN CREATE SOME SPORADIC BEHAVIOR. BUT ALSO THUNDER CLOUDS WITH LIGHTNING STRIKES IS A CONCERN. >> Reporter: CLIMATE CHANGE HAS MADE CALIFORNIA SUMMERS HOTTER AND DRIER, INCREASING THE FREQUENCY OF LARGE FIRES BY AN ESTIMATED 25%. THE SIZE OF THE LINE FIRE AND THE SMOKE-FILLED AIR, FORCED PEOPLE IN THE MOUNTAIN COMMUNITIES OF RUNNING SPRINGS AND ARROW BEAR LAKE TO EVACUATE. >> THE SMOKE WAS COMING IN REALLY FAST. IT WAS JUST ALL OF A SUDDEN REALLY, REALLY FAST. >> Reporter: JULIA BUSH AND HER SISTER, CASANDRA HAVE MOVED THREE TIMES TO ESCAPE THE SMOKE AND FIRE. FIRST FROM THEIR HOMES, THEN TO TWO DIFFERENT EVACUATION CENTERS. >> SIRENS WERE GOING OFF, AND SPEAKERS WERE GOING, GET OUT, BASICALLY. >> Reporter: THEY'RE NOW AT A RED CROSS CENTER, WHICH HAS TRIPLED ITS CAPACITY. JULIE AND HER FAMILY SAY THEY'RE JUST RELIEVED THAT THEY'RE SAFE. >> FAMILIES OUT. WE'RE ALIVE. THAT'S THE NUMBER ONE THING. >> Reporter: NOW TEMPERATURES HERE TODAY ARE EXPECTED TO SOAR TO ABOUT 100 DEGREES. SO IT'S GOING TO BE ANOTHER GRUELING DAY ON THE FIRE LINES FOR FIREFIGHTERS. >> BEN, YOU SPOKE TO SOME RESIDENTS WHO WERE RELIEVED TO HAVE A PLACE TO GO, BUT YOU'VE COVERED ENOUGH OF THESE STORIES, YOU KNOW SOME PEOPLE JUST WANT TO STAY UNTIL THE LAST MINUTE OR NOT LEAVE AT ALL. WHAT HAVE YOU BEEN HEARING FROM RESIDENTS? >> Reporter: YEAH, THERE ARE SOME PEOPLE WHO CHOSE NOT TO EVACUATE. THERE ARE OTHER FOLKS WHO THOUGHT THEY WEREN'T GOING TO EVACUATE, THEN THIS FIRE CHANGED SO DRAMATICALLY AND SO QUICKLY OVER THE WEEKEND, WHERE IT REALLY JUST BLEW UP FROM, YOU KNOW, 3,000 ACRES TO THEN 7,000 ACRES, TO THEN 15,000 ACRES. IT JUST KEPT DOUBLING. SO THAT REALLY CAUGHT SOME PEOPLE BY SURPRISE WHO THOUGHT THEY WERE GOING TO BE FINE. THEY THEN GOT IN THEIR CARS AND GOT OUT OF DODGE, BECAUSE THE LAST THING YOU WANT TO DO IS BE UP IN A