Crews were helped by the arrival of monsoonal moisture from the Gulf of Mexico, lowering temperatures, increasing the humidity and bringing light rain.
Officials remained on guard, however, in case the weather system brings lightning strikes, or heavy rain that could cause flash flooding.
The Mountain fire, which began last Monday, has destroyed or damaged more than a dozen structures including some homes in the Bonita Vista and Pine Springs areas.
The Mountain fire has burned through 27,000 acres. A portion of the fire is near the Palm Springs Aerial Tramway, and half a dozen crews were defending that area.
To the west, firefighters have a better handle on the 700-acre Rancho fire near the Grapevine, which forced the brief closure of Interstate 5 on Friday. No structures have been damaged in that blaze but evacuations near the Lebec town center remain in effect.
Crews have 85% of that blaze surrounded.
Humid conditions were expected to last in Southern California through Monday.
Light rain in the Los Angeles Basin and Orange County was expected to bring precipitation of 0.15 inches.
Most places won't see enough rain to scratch summer picnic plans, but a handful of areas could see a stray thunderstorm that could dump as much as half an inch of rain, "and there's no way we can pinpoint where that is," said Miguel Miller, a National Weather Service forecaster in San Diego.
"I wouldn't cancel plans," Miller said, "but it's something to certainly be aware of. If you're out somewhere, you might need to pick up quickly."
The increased humidity and cloud cover have brought temperatures down into the 70s in the L.A. Basin and 80s in the valleys.
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