Monsoon storms head for Southern California, easing the heat but raising fire fears

The heat that has gripped Southern California is set to give way to something more turbulent. Forecasters say monsoonal moisture is moving into the region, bringing the season's first real chance of thunderstorms, and a mix of relief and risk.

What's coming

The National Weather Service expects moisture to surge north into Southern California, raising the chance of showers and thunderstorms into the weekend and the following week, according to its forecasters. The odds on any given afternoon are modest, but the pattern is a clear break from the hot, dry high-pressure system that has dominated. Storms are most likely over the mountains and deserts, with inland valleys seeing a lesser chance and the coast staying mostly dry.

Why storms can mean fire

Monsoon storms in California come with a paradox: they bring rain, but also lightning, and lightning is one of the ways wildfires start. After a long, hot spell that has left vegetation parched, a strike in the backcountry can ignite a blaze even as rain falls nearby, especially if a storm produces more lightning than water. Forecasters watch these setups closely for exactly that reason.

Flooding, too

There is a second hazard. Intense monsoon cells can drop heavy rain quickly, and in areas scarred by past wildfires, that water runs off rather than soaking in, raising the risk of flash flooding and debris flows. It is the kind of threat that can turn a brief, localized downpour into a dangerous situation in the wrong spot.

The heat eases

The upside is real. As the pattern shifts and moisture moves in, the extreme heat that prompted advisories across inland and desert areas is expected to ease, forecasters said. Humidity will rise, which is its own kind of discomfort, but the dangerous triple-digit highs should back off in many spots.

What to do

Forecasts this far out are uncertain, and exactly where and when storms fire is hard to pin down. Residents in the mountains and deserts, in particular, should keep an eye on the sky and on local alerts in the afternoons and evenings, when storms are most likely, and heed the standard advice when thunder rumbles: head indoors. For a region weary of the heat, the coming days offer a change, and a reminder that in a California summer, weather relief rarely comes without a catch.