SAN FRANCISCO (AP) -- Firefighters struggled to contain a wildfire exploding in northeastern California under blazing temperatures as another heat wave hit the U.S. West this weekend, prompting an excessive heat warning for inland and desert areas.
The Beckwourth Complex -- two lightning-caused fires burning 45 miles north of Lake Tahoe -- showed no sign of slowing its rush northeast from the Sierra Nevada forest region after doubling in size between Friday and Saturday.
California's northern mountain areas already have seen several large fires that have destroyed more than a dozen homes. Although there are no confirmed reports of building damage, the fire prompted evacuation orders or warnings for roughly 2,800 people along with the closure of nearly 200 square miles of Plumas National Forest.
On Friday, hot rising air formed a gigantic, smoky pyrocumulus cloud that reached thousands of feet high and created its own lightning, fire information officer Lisa Cox said.
Spot fires caused by embers leapt up to a mile ahead of the northeastern flank — too far for firefighters to safely battle — and winds funneled the fire up draws and canyons full of dry fuel, where "it can actually pick up speed," Cox said. The flames rose up to 100 feet in places, forcing firefighters to focus instead on building dozer lines to protect homes.
Firefighters usually take advantage of cooler, more humid nights to advance on a fire, Cox said, but the heat and low humidity never let up. The more than 1,200 firefighters were aided by aircraft. But the blaze was expected to continue forging ahead.
The air was so dry that some of the water dropped by aircraft evaporated before reaching the ground, she added.
"We're expecting more of the same the day after and the day after and the day after," Cox said.
The blaze, which was only 8% contained, increased dramatically to 86 square miles (222 square kilometers) after fire officials made better observations.
It was one of several threatening homes across Western states that are expected to see triple-digit heat through the weekend as a high-pressure zone blankets the region.
The National Weather Service warned the dangerous conditions could cause heat-related illnesses, while California's power grid operator issued a statewide Flex Alert from 4 p.m. to 9 p.m. Saturday to avoid disruptions and rolling blackouts.
The California Independent System Operator warned of potential power shortage, not only because of mounting heat, but because a wildfire in southern Oregon was threatening transmission lines that carry imported power to California. Gov. Gavin Newsom issued an emergency proclamation on Friday suspending rules to allow for more power capacity, and the ISO requested emergency assistance from other states.
Pushed by strong winds, the Oregon fire doubled in size to 120 square miles (311 square kilometers) Saturday as it raced through heavy timber in the Fremont-Winema National Forest near the Klamath County town of Sprague River.
NV Energy, Nevada's largest power provider, also urged customers to conserve electricity Saturday and Sunday evenings because of the heat wave and wildfires affecting transmission lines throughout the region.
In Southern California, a brush fire sparked by a burning big-rig in eastern San Diego County forced evacuations of two Native American reservations Saturday.
In north-central Arizona, Yavapai County on Saturday lifted an evacuation warning for Black Canyon City, an unincorporated town 43 miles north of Phoenix, after a fire in nearby mountains no longer posed a threat.
A wildfire in southeast Washington grew to almost 60 square miles (155 square kilometers) as it blackened grass and timber while it moved into the Umatilla National Forest.
In Idaho, Gov. Brad Little declared a wildfire emergency Friday and mobilized the state's National Guard to help fight fires sparked after lightning storms swept across the drought-stricken region.
Fire crews in north-central Idaho were fighting three lightning-sparked wildfires covering a combined 62 square miles. The blazes threatened homes and forced evacuations in the tiny, remote community of Dixie about 40 miles southeast of Grangeville.
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