Dry Lightning Sparks Concern as Bay Area Braces for Potential Grass Fires

A day after hundreds of lightning strikes ignited several fires across the San Joaquin Valley and Sierra foothills, forecasters warned Bay Area residents about the potential threat of lightning through Tuesday evening.

The mass of moisture moving north will bring a 15% chance of thunderstorms from Morgan Hill to Napa, but it’s not expected to produce much precipitation, said Rachel Kennedy, a National Weather Service meteorologist. With that dry lightning — and temperatures reaching 90 degrees in parts of the Bay Area — each strike, a potential spark can ignite devastating grass fires.

“We’re in fire season now, so everybody’s got to pay attention,” Kennedy said.

The potential for thunderstorms, fueled by the remnants of Tropical Storm Alberto and some monsoonal flow from the southeast, will move to the North Bay as the day progresses, she said.

Kennedy is particularly concerned about dry lightning because recent heat waves have dried out much of the grass on the region’s golden hills, leaving prime fuel for fire. At least a dozen wildfires started Monday, mainly in the foothills of the Sierra Nevada, as more than 1,000 dry lightning strikes hit the area.

“The fire risk is pretty much for the entire Bay Area,” she said.

Grass fires can be as harmful as forest fires and burn fast and hot, Kennedy said. Such dry fuels drove the Point Fire, which is now 100% contained after burning 1,207 acres and destroying multiple structures near Lake Sonoma.

The threat of lightning will diminish overnight, and a cooling pattern will start, dropping temperatures about 10 degrees, Kennedy said. She expects the region to heat up by next week, just in time for the Fourth of July.

“Temperatures do look like they’re going to rise quite a bit with widespread highs in the upper 80s to mid-90s,” she said.