Chris Caskey, The Union Democrat

With unusually stormy weather kicking off the week, local fire officials are still on the lookout for lingering blazes sparked by lightning strikes.

The Mother Lode saw a string of storms overnight Sunday and into Monday as unseasonable weather conditions brought moist, unstable air into the area. The storms brought with them lightning that peppered the central Sierra foothills with small fires and knocked power out to some residents.

The storms also dropped small amounts of rain in some spots as well, breaking a local record.

"It's kind of rare," National Weather Service meteorologist Stefanie Henry said of the stormy weather this time of year. "We do get low pressure coming in all summer long, but they're usually dry. It's pretty rare to get … thunderstorms."

The stormy weather was caused by warm, moist air coming from the south, a high pressure system to the east and low pressure off the coast, she said. The storms stayed to the east of the Sierras Sunday until after dark, then appeared as far west as the Central Valley by the early morning.

Along with the lightning and thunder, the storms dropped 0.02 inch of rain in Sonora and Jamestown, and 0.16 inch in Angels Camp. The Sonora total is a record for Sunday and Monday, with the previous precipitation record at zero, according to weather data provided to The Union Democrat.

The unsettled weather is expected to be gone by today, with a cooling trend likely to drop temperatures as low as the upper 80s by later this week, according to the National Weather Service.

Even though the lightning is gone and the weather is cooling, area fire officials remained on alert Monday and will continue dealing with lingering effects. Cal Fire spokeswoman Lisa Williams said fire crews worked to extinguish six lightning-caused blazes, mostly in Calaveras County, into Monday. Two of them were contained by the morning, one located off Railroad Flat Road and another near San Andreas. Both were less than an acre, and neither threatened any structures, Williams said.

Crews continued fighting fires near New Melones, Copperopolis and Big Trees State Park. The largest as of Monday afternoon was a 75-acre blaze near the Saddle Creek Golf Course that was 75 percent contained by about 5 p.m.. None of the fires damaged any structures as of late Monday afternoon.

Williams said air patrols were flying over both Tuolumne and Calaveras counties Monday looking for blazes, and crews will be stationed at the Blue Mountain lookout to spot smoke at least until Wednesday.

Even though the storms were accompanied by rain, Williams said there was not enough precipitation to saturate the ground and cancel out the fire danger - especially considering this has been a drier than average year.

"Even though the system has moved on, we can have what we call sleepers," she said.

Some residents also dealt with power outages due to the storms Monday morning. According to PG&E, about 40 customers in Copperopolis, San Andreas, Sonora, Twain Harte and West Point were affected Monday.