Near-record temperatures and the threat of dry lightning have prompted a "red flag warning" regarding fires, issued for today by the National Weather Service.

Fire officials are already throwing every resource available at fires as soon as they are reported in an effort to prevent a catastrophic blaze.

Fire engines, air tankers, helicopters, spotter planes and inmate hand crews responded to three fires in Tuolumne and Calaveras counties Wednesday afternoon and at least one more this morning.

The scorching heat is also testing California's power reserves. California's Independent System Operator, which oversees the state's power grid, is expected to announce the third straight day of power conservation alerts by this afternoon.

State regulators said this morning they didn't expect to order the rolling blackouts that left thousands without power last year, said ISO spokeswoman Stephanie McCorkle.

The most serious fire Wednesday, reported at 3:40 p.m., destroyed a custom home off the 19600 block of Ferretti Road.

California Department of Forestry and Fire Protection (CDF) investigator Rommie Jones said the value of the home, which was being remodeled, had not been determined this morning, but may be $1 million or more. The cause is under investigation.

The home was owned by Doug Roach of Auburn. No one was there when the fire started, said Jones.

Because of its remote location on the edge of the Tuolumne River canyon, he added, the house was fully engulfed before firefighters arrived.

The fire spread to nearby wildland, but was held to one acre of grass, said Jones.

Responding to that fire were Groveland Community Services District, California Department of Forestry and Fire Protection, Tuolumne County Fire Department, three inmate crews from Baseline Conservation Camp and two air tankers, a helicopter and an air attack spotter plane from Columbia Air Attack Base.

Sparks from a riding lawn mower started a two-acre grass fire on the 16890 block of Old Priest Grade that was reported at 1:45 p.m. Wednesday.