For the first time in months, widespread rainfall is drenching the Los Angeles area as a strong band of moisture from a dissipated tropical storm moves north. <\/p>\n
By Thursday morning, much of Southern California had already recorded some measurable \u2014 though mostly minor \u2014 rainfall, while a few inland areas were experiencing localized flooding that officials warned could get worse and expand. Much of the region remains under a flood watch<\/a> through early Friday. <\/p>\n \u201cAs the day wears on \u2026 we could definitely start getting those heavier showers and thunderstorms developing,\u201d said Rich Thompson, a meteorologist with the National Weather Service in Oxnard. \u201cSome areas will have a lot of rain.\u201d<\/p>\n Wet storms across Southern California in September are unusual, but not unheard of, Thompson said. Monsoonal storms from the east \u2014 usually confined to the mountains and deserts \u2014 are more typical this time of year, he said, but every once in a while a tropical storm from the eastern Pacific pushes north, bringing bands of rain. <\/p>\n FLOOD WATCH in effect for sections of #SoCal<\/a> with biggest concern for the recent burn scars. <\/p>\n – Showers\/thunderstorms expected thru Thu night \u2014 NWS Los Angeles (@NWSLosAngeles) September 17, 2025<\/a><\/p><\/blockquote>\n On Wednesday, remnants of former Tropical Storm Mario started to move into Southern California, boosting humidity and the chance for showers and thunderstorms.<\/p>\n The most significant rainfall and strongest storms were forecast for Thursday. Most populated areas of Los Angeles, Orange, San Diego and Ventura counties can expect to get up to a quarter- to a half-inch of rain, while some mountain and desert areas could see up to an inch, according to the National Weather Service. <\/p>\n But some areas could get as much as 2 inches of rain locally, depending on the strength and location of the developing storms. Under certain circumstances, officials are warning of storms that could bring dangerous lightning, gusty and erratic winds and heavy rains that could cause localized flooding.<\/p>\n \u201cRainfall rates capable of causing flash flooding, mud, and debris flows have already occurred earlier this morning, and daytime heating will only serve to destabilize the environment later today,\u201d the National Weather Service posted in its Thursday forecast discussion<\/a>.<\/p>\n The Santa Monica Mountains and much of the inland Southern California remain under a flood watch through early Friday, with rain rates reaching up to a half-inch per hour in some areas \u2014 or possibly higher. The National Weather Service warned that \u201cexcessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations.\u201d <\/p>\n In San Bernardino County, officials issued a more elevated flood advisory Thursday morning, saying that Twentynine Palms and the Yucca and Morongo valleys \u201cwill experience flooding,\u201d having already received half an inch of rain, and more on the way.<\/p>\n Officials there were responding to \u201cminor flooding and accidents due to wet roads on State Route 62,\u201d the advisory said<\/a>. Some local residents reported flooded roads in and around Twentynine Palms. <\/p>\n Flooding concerns would extend further north into Friday, with parts of the Central Valley, Sierra Nevada and its surrounding foothills also under a flood watch. <\/p>\n While some mountain and desert areas have seen recent precipitation from monsoonal storms, downtown Los Angeles hasn\u2019t had any measurable rainfall since early May, according to the National Weather Service. <\/p>\n But despite the widespread rains Thursday, officials said it likely wouldn\u2019t be enough to pull southwestern California out of \u201csevere drought\u201d conditions, which the region has remained in since March, according to the the U.S. Drought Monitor<\/a>. It\u2019s also likely not enough to eliminate the threat of another punishing wildfire season \u2014 often most dangerous during the upcoming Santa Ana winds season.<\/p>\n \u201cIt\u2019s nice to have this rain, every little bit helps,\u201d Thompson said. \u201cBut in terms of impacts on fire season \u2026 this would have a very marginal effect.\u201d<\/p>\n Fire officials typically don\u2019t consider the threat for fires diminished until at least 2 to 4 inches of rain has fallen, and only a few isolated areas might get 2 inches from this tropical moisture. <\/p>\n But, Thompson said there could still be some benefit. <\/p>\n \u201cIt might slow things down a little bit the next week or two,\u201d he said. <\/p>\n Early Thursday morning, downtown Los Angeles, UCLA, Anaheim, Oceanside and Palm Springs had already recorded around a tenth of an inch of rain, according to the National Weather Service. <\/p>\n A few places had seen a bit more: Carlsbad and Chula Vista received almost a quarter-inch; San Diego International Airport and Coronado saw almost a half-inch; Riverside had seen three-tenths of an inch. <\/p>\n These totals will likely increase as the day goes on. <\/p>\n But even when rain isn\u2019t falling, Southern California will feel the effects of the moist air mass over the region. Forecasters noted that atmospheric moisture readings from San Diego almost mirrored those from Key West on Thursday \u2014 or about 200% of normal for Southern California. <\/p>\n \u201cIt will be muggy out there,\u201d the weather service warned<\/a>. \u201cOff and on again showers to continue as well, with isolated thunderstorms. Expect slick roads.\u201d<\/p>\n While Los Angeles should dry out by Saturday, forecasts show that there\u2019s the potential for another round of tropical weather next week, but it\u2019s too early to tell what will materialize. <\/p>\n Long-range forecasts published this week predict that Southern California could remain in an above-average rainfall pattern for the next week<\/a>, but it likely won\u2019t last. Precipitation outlooks for the month of October<\/a> \u2014 which marks the officials start of California\u2019s rainy season \u2014 did not show an uptick in rainfall.<\/p>\n And forecasters are expecting a La Ni\u00f1a cycle to emerge soon<\/a> and remain in place through December, a shift in climate patterns that historically swings the state toward drought, especially in Southern California<\/a>. <\/p>\n Times staff writer Alex Wigglesworth contributed to this report.<\/p>\n \n
– Rainfall rates could exceed 0.50″ per hour
– Mud\/debris flows possible in and around recent burn areas#CAwx<\/a> pic.twitter.com\/5qJFzGUksz<\/a><\/p>\n