Lakeside firefighters Joe Vasquez, left, and David Csik walk around a house as Lakeside Fire Capt. Jon Jordan watches large flames burn toward the home on Highway 94 south of Potrero Calif., on Monday, June 20, 2016. An intensifying heat wave stretching from the West Coast to New Mexico threatened to make the fight against Southern California wildfires more difficult Monday. (Hayne Palmour IV/San Diego Union-Tribune via AP)

Lakeside firefighters walk next to a home on Highway 94 south of Potrero, Calif., as a wildfire burns near the home on Monday, June 20, 2016. An intensifying heat wave stretching from the West Coast to New Mexico threatened to make the fight against Southern California wildfires more difficult Monday. (Hayne Palmour IV/San Diego Union-Tribune via AP)

The California state flag flies next to a home on Highway 94 south Potrero, Calif., on Monday, June 20, 2016, as huge flames roar behind it. An intensifying heat wave stretching from the West Coast to New Mexico threatened to make the fight against Southern California wildfires more difficult Monday. (Hayne Palmour IV/San Diego Union-Tribune via AP)

Lakeside firefighter Joe Vasquez watches as large flames burn next to a home on Highway 94 south of Potrero, Calif., on Monday, June 20, 2016. An intensifying heat wave stretching from the West Coast to New Mexico threatened to make the fight against Southern California wildfires more difficult Monday. (Hayne Palmour IV/San Diego Union-Tribune via AP)

The California state flag flies next to a home on Highway 94 south Potrero, Calif., on Monday, June 20, 2016, as huge flames roar behind it. An intensifying heat wave stretching from the West Coast to New Mexico threatened to make the fight against Southern California wildfires more difficult Monday. (Hayne Palmour IV/San Diego Union-Tribune via AP)

Upland firefighters, from left, Nima Homayounieh, Joseph Armendariz, and Capt. Joe Burna, watch as flames burn toward Highway 94 near Potrero, Calif., on Monday, June 20, 2016. (Hayne Palmour IV/San Diego Union-Tribune via AP)

Upland Fire Capt. Joe Burna watches as a tanker drops fire retardant to stop a wildfire from jumping over Highway 94 near Potrero, Calif., on Monday, June 20, 2016. (Hayne Palmour IV/San Diego Union-Tribune via AP)

Two fire captains with the Loma Linda Fire Department watch as a tanker flies in low to drop fire retardant on a wildfire burning close to Highway 94 near Potrero, Calif., on Monday, June 20, 2016. (Hayne Palmour IV/San Diego Union-Tribune via AP)