Rain and cooler temperatures will bring relief to Southern California this weekend, after a prolonged stretch of dry, breezy weather that allowed wildfires to thrive.

The parched landscape between Los Angeles and San Diego hasn’t seen any significant precipitation so far this winter, providing plenty of dry vegetation to fuel the fires. A cold storm system forecast to move across the region Saturday through Monday will change that.

But there’s a growing chance that the rain could be on the heavier side — up to three quarters of an inch per hour, said Ryan Kittell, a National Weather Service meteorologist. That could trigger flash floods and debris flows in places recently charred by the Palisades and Hughes fires and especially in the region burned by the Eaton fire, which is expected to see more rain than the other areas.

The Santa Ana winds that have swept over the region for weeks finally stopped blowing late Friday morning and a coastal breeze developed, pushing moist cool air off the ocean.

Light showers could fall as early as Saturday afternoon in Los Angeles and Ventura Counties, where fires are still burning. The greatest chance for heavier rainfall will come between 4 p.m. Sunday and noon Monday. Parts of Los Angeles, including downtown, could receive as much as an inch of rain, said Brian Lewis, a Weather Service forecaster in Oxnard, Calif.

“We’re not expecting high rainfall rates unless a thunderstorm goes right over that area,” he said. There’s now a 15 to 25 percent chance of isolated thunderstorms.

There’s also a chance for snow at elevations as low as 3,500 feet. The lower parts of the San Gabriel and San Bernardino Mountains could receive up to four inches of snow. Elevations above 5,000 feet could see six to 12 inches, with as much as two feet on the highest peaks.

Though the risk for debris flows — or mudslides — is relatively low, officials were deploying crews across the region this week to clear debris and deploy sandbags. At a news conference, Mark Pestrella, Los Angeles County’s public works director, said that people living on or near scorched hillsides should be cautious, especially if their homes had not been inspected after the fires.

“Your best bet is not to be in that home when it rains,” he said.

Mudslides or debris flows — which Jason Kean, a research hydrologist with the U.S. Geological Survey, described as “a flood on steroids” — happen when burned soil becomes compact like concrete, funneling water down slopes that have lost any vegetation to keep it in check. That rushing water can claw up the landscape, unleashing a torrent of trees, rocks, brush and anything else in the way. Residents can use burn maps created by the U.S.G.S. to determine if their home is at risk. The Eaton fire near Pasadena could be the most prone to debris flows. Peak rainfall — defined as more than 1.5 inches per hour, falling within a 15-minute interval — would be nearly certain to trigger a debris flow, the maps show.

The San Diego area will see the effects of the storm about 12 hours after Los Angeles, as the chance for rain, and chillier air, moves south on Sunday and Monday.

While the projected precipitation totals for the region went up slightly on Friday than earlier predictions, Rich Bann, a meteorologist with the Weather Service, said this storm wouldn’t deliver a major deluge.

“In most areas at most times, this amount of rain generally isn’t a concern and it’s only a concern right now because we have these fresh burn scars,” he said.