Dry lightning and gusty winds forecast for Sonoma, Lake and Mendocino counties put local fire officials on high alert Sunday.

Low humidity, erratic winds between 20 and 30 mph and a dry storm system arriving from the southwest prompted the National Weather Service to issue a red flag warning for much of northern California, starting at 11 a.m. Monday and lasting until 11 p.m. Wednesday.

"We staffed all of our engines and brought in all of our reserve engines in preparation," said Cal Fire Capt. Jesse Torres with the Mendocino command center in Willits.

"The biggest danger is lightning," National Weather Service meteorologist Steve Anderson said.

The warning follows a dry spring and comes amid an active fire season in California, during which 5,000 firefighters have battled 10 wildfires.

"This is the fifth lightning scare this year," Torres said.

Two Mendocino engines have joined about 700 firefighters battling a Butte County blaze that threatens 400 structures and has forced hundreds of people to evacuate.

Smoke from the nearly 3-square-mile Swedes Fire, which was 45 percent contained late Sunday, clouded skies, according to Cal Fire.

In Lake County, the Double Fire near Clearlake Oaks was 100 percent contained by 5 p.m. Sunday. Crews planned to return Monday to check on the burned area off Highway 20 and Mule Skinner Road, Cal Fire dispatchers said.

The dry storm system forecast to arrive Monday prompted a warning that stretched from Mendocino to Monterey. For Sonoma and Mendocino counties, the areas of most concern were inland, with coastlines excluded, said Anderson. In Southern California, more than 10,000 lightning strikes hit Sunday.

"We expect some (in northern California), but not the big lightning storms going on down south," Anderson said.