TENS OF THOUSANDS OF BUILDINGS AND HOMES NOW AT RISK. DANA GRIFFIN IS THERE. >> Reporter: TONIGHT, THOUSANDS FORCED TO EVACUATE AS THE LINE FIRE BURNING IN SAN BERNARDINO COUNTY THREATENS 35,000 HOMES AND BUILDINGS. >> SO AS FAR AS FIRES THIS SUMMER, THIS ONE RANKS UP THERE BECAUSE OF THE UNPREDICTABILITY. IT MIGHT NOT BE THE BIGGEST IN ACREAGE, BUT WE HAVE PEOPLE IN FRONT OF IT AND IT'S VERY UNPREDICTABLE MAKING IT THAT MUCH MORE DANGEROUS. >> Reporter: THE AREA UNDER A STATE OF EMERGENCY LOCATED IN THE MOUNTAINS 60 MILES EAST OF LOS ANGELES. THE FIRE FUELED BY UNPREDICTABLE THUNDERSTORMS, STEEP TERRAIN AND SCORCHING TEMPERATURES WITH 300 LIGHTNING STRIKES SATURDAY ALONE. RAIN IN THE AREA HAS HELPED A BIT BUT THE THREAT IS NOT OVER. IN NEVADA, THE DAVIS FIRE ALSO FORCING HUNDREDS TO EVACUATE. >> KEEP GOING, GUYS, KEEP GOING. >> Reporter: DOZENS OF HORSES SEEN HERE RUNNING ALONGSIDE A SMOKY ROADWAY. FLAMES THERE BURNING 1500 ACRES SETTING ABLAZE HOMES AND OTHER STRUCTURES. MEANWHILE, 30 MILLION ARE UNDER HEAT ALERTS ACROSS THE WEST. A 3-YEAR-OLD DIED IN ANAHEIM, CALIFORNIA WHILE INSIDE A HOT CAR WITH HER MOTHER. ALSO FOUND UNCONSCIOUS IN THE VEHICLE. >> BACK HERE IN THE FIRE ZONE, OFFICIALS SAY THEY ARE LINING CREWS ON ALL SIDES O