FRESNO — Firefighting crews tried to corral a fast-growing blaze churning through central California’s Sierra National Forest as forecasters warned Tuesday that lightning strikes from thunderstorms could spark new ignitions.

Since breaking out Sunday afternoon, the Garnet Fire has scorched 14 square miles of grass, chaparral and timber in a remote area known for camping and hiking about 60 miles east of Fresno. There was no containment.

RELATED: Map: Garnet Fire evacuations in national forest east of Fresno

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Firefighters were aided by scattered rain showers as they worked to protect the tiny Balch Camp community and nearby hydroelectric facilities along the Kings River, according to a Tuesday incident report.

“However, continued strong, erratic winds on top of dry, heavy vegetation will likely test containment efforts,” the report said.

Parts of central and northern California are under red flag warnings for increased fire threat from dry lightning that could accompany thunderstorms, the National Weather Service said.

The 10-square-mile Pickett Fire in Napa County wine country saw little growth Monday as crews kept flames contained to canyons about 80 miles north of San Francisco. It was 17% contained on Tuesday.

There have been no reports of damage to any vineyards from the fire, a spokesperson for the trade group Napa Valley Vintners said Monday.

In central Oregon, rain and cooler temperatures helped crews make progress against the Flat Fire, which has charred 34 square miles of rugged terrain in Deschutes and Jefferson counties since igniting in dry, hot weather last Thursday. It was 7% contained on Tuesday.

“The incident, for the first time in the last three days, is really beginning to stabilize,” Travis Medema, the state’s chief deputy state fire marshal, told a community meeting Monday night.

Authorities at one point ordered evacuations for more than 4,000 homes but lifted orders for some areas on Monday.