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The Latest: Hotter days bring bigger fire challenges to West

  • A tanker drops fire retardant as a wildfire burns along Highway 94 near Potrero Calif., on Monday, June 20, 2016. (Hayne Palmour IV/San Diego Union-Tribune via AP)

    A tanker drops fire retardant as a wildfire burns along Highway 94 near Potrero Calif., on Monday, June 20, 2016. (Hayne Palmour IV/San Diego Union-Tribune via AP)  (The Associated Press)

  • 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 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)  (The Associated Press)

  • 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)

    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)  (The Associated Press)

The Latest on wildfires burning in the West (all times local):

7:50 a.m.

Southern California firefighters are in for another day of brutal conditions as they battle wildfires.

The National Weather Service says Monday will be the peak of the heat wave that has already brought record-breaking, triple-digit heat to the region.

Despite the conditions, firefighters report a slight increase in containment of the fire burning in rugged terrain west of Santa Barbara since last week.

The blaze is now 54 percent surrounded and remains at just over 12 square miles.

Southeast of San Diego, however, a wildfire near the town of Potrero grew by several hundred acres overnight and is now estimated at nearly 3 square miles, with just 5 percent containment.

Significant fires are also burning in New Mexico and Arizona.