An upper level low combined with monsoonal moisture produced numerous thunderstorms, which resulted in several reports of heavy rainfall, flooding, and severe wind. Most of the impacts occurred on the afternoon of August 25th over the mountains, deserts, and inland valleys.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS SGX wrote it up.
An upper level low combined with monsoonal moisture produced numerous thunderstorms, which resulted in several reports of heavy rainfall, flooding, and severe wind. Most of the impacts occurred on the afternoon of August 25th over the mountains, deserts, and inland valleys.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS San Diego, CA wrote its last area forecast discussion before the first event at Aug 25, 7:35 AM PST, 3 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service San Diego CA 835 AM PDT Mon Aug 25 2025 .SYNOPSIS... Thunderstorms develop today over the mountains and deserts with heavy rainfall rates at times potentially exceeding 1"/hr. Afternoon monsoon thunderstorms will be possible both Tuesday and Wednesday as well, with more constricted coverage in the mountains. A pattern change for the latter half of the week will limit thunderstorms after Wednesday, with more seasonable temperatures and a deepening marine layer. By the weekend and into early next week, a warming trend sets in and temperatures return above normal. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .UPDATE... The main moisture corridor for this afternoon looks to stretch from Imperial County up through the Anza-Borrego Desert and into the Santa Rosa Mountains. Rainfall rates in this region may exceed 1"/hr at times, especially in the early afternoon. Storms look to develop along the spine of the mountains beginning around noon, with some cells strong enough to make it off the mountains and into the urban areas on the eastern sides. While the main moisture corridor will be further south, if any storms manage to develop off the San Bernardino Mountains, rainfall rates may exceed 0.5"/hr at times. Flash flooding will be the main concern with storms today, but also very gusty and erratic winds as these storms move off the mountains, potentially exceeding 60 mph. Low chances for any storms/rain to make it into the San Diego urban areas or Inland Empire this afternoon. Other than the mountains, the areas most likely to see impacts from storms today include the San Diego County Deserts and the Coachella Valley. Storms will be diurnally driven, with most activity dying off after 6PM. && .PREVIOUS DISCUSSION FROM 238 AM... Today through tonight... The subtropical ridge continues to dominate the region with above average temperatures and recycled monsoonal moisture in the mid to upper levels will also again provide a chance of thunderstorms over the mountains and deserts during the afternoon and early evening hours. Given the very weak flow out of the south at the 700 mb level, it is likely that any showers and storms that develop later today over the higher terrain due to orographic lifting will struggle to move off into the adjacent valleys and deserts. There is still enough instability over the deserts to allow for another possible strong storm, similar as to what there was yesterday over Imperial. Bases of associated CBs with these storms will be quite elevated with the classic "inverted V" sounding, signifying a lot of drier air aloft and DCAPE alludes to the possibility of some of these storms producing gusty outflow winds due to dry microbursts. There could also be some small hail, especially over the deserts where there are higher MUCAPE values. There could also be brief periods of heavy rain, small hail, dangerous cloud-to- ground lightning, and gusty and erratic winds, regardless if there are any dry microbursts produced. There even exists the slight chance of a "heat burst" happening again, similar to what happened a could of days ago with the inland valleys becoming much warmer than surrounding areas, given the amount of dry air aloft and the presence of a strong inversion west of the mountain ranges. Temperatures will be similar today, perhaps a degree or two cooler for some locations. The marine layer will likely remain partially eroded out from over the inner coastal waters this morning as it currently is due to mid level clouds passing overhead. There could be some patchy areas of fog this morning, especially within some of the valleys along the I-15 corridor. Tomorrow through the upcoming weekend... For tomorrow, the subtropical ridge axis will begin to shift more towards the east and allow for troughing upstream from the northwest to begin to edge closer to SOCAL ever so slowly and begin a gradual cooldown that will continue through the rest of the week, with temperatures returning to more normal values tomorrow. The monsoon moisture will become more confined to the east, although there could be an isolated storm or two still developing over the mountains and possibly the adjacent deserts tomorrow during the afternoon hours, otherwise tomorrow will begin a drying trend with a lesser chance of mountain/desert thunderstorms going into the latter part of the week. Temperatures will be cooler tomorrow, and closer to the seasonal average for this time of year, and then temperatures will remain nearly steady throughout the rest of the week and going into the weekend. Most of the deterministic models keep a very slight chance of convection over the mountains/deserts during the afternoon hours, although it will likely be only over a few isolated areas where there is higher terrain, such as the San Bernardino Mountains. The CWA should be mostly dry and clear for the upcoming weekend. The marine layer will begin to deepen and extend further inland overnight with a more persistent onshore flow by later in the week. && .AVIATION... 251500Z...Coast/Valleys...Patchy low clouds based 800-1100 feet MSL are clearing to the coast with full clearing by 17z. Mid and high level clouds AOA 10,000 ft, otherwise, VFR conditions. Clouds redeveloping after 26/04Z with bases around 900-1200 ft MSL making it 15-20 miles inland by 12z. Mountains/Deserts...50-70% chance of +SHRA/TSRA over the mountains and a 35-50% chance over the deserts between 19-02Z. CB bases near 12 kft and tops to 30 kft. Gusty outflow winds higher than 35 kts, 1- 3 SM vis in +RA, small hail, and lightning are possible. CB/SHRA dissipating this evening. && .MARINE... No hazardous marine conditions are expected through Friday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && PUBLIC...Zuber AVIATION/MARINE...Westerink
The San Diego radar (KNKX), 41 km away, was scanning. The volume nearest the first event began at 18:58 UTC.
7 heavy rain, 5 thunderstorm wind, 3 flood, 2 debris flow. Local standard time, as filed.
Mesonet station 5.9 miles W Pine Valley recorded 0.79 of rain over a 2 hour period ending around 2 PM PDT.
A mesonet station 5 miles WNW of Pine Valley reported a 58 mph wind gust associated with outflow from a thunderstorm.
Mesonet station PNVC1 0.8 SW Pine Valley recorded 0.79 of rain with 0.70 falling in 30 minutes from 11:50-12:30 PDT.
Mesonet station FW0527 Guatay Spider Mountain recorded 1.11 of rain with 0.93 falling in one hour.
Agua Caliente ALERT gauge reported 1.13 inches of rain in 1 hr 20 min due to a thunderstorm.
Mesonet station AGUC1 Agua Caliente recorded 1.17 of rain in a short time frame with 0.86 falling in one hour from 1:40-2:40 PM PDT.
Mesonet station 4 miles SSW Pine Valley recorded a 62 mph wind gust associated with outflow from a thunderstorm in the vicinity.
Palm Canyon Creek ALERT gauge reported 1.30 inches of rain in 33 minutes due to a thunderstorm. A total of 1.42 inch was reported.
Mesonet station 5 miles SSE Lucerne Valley recorded a 58 mph wind gust associated with thunderstorm outflow.
Mesonet station PRRSR Perris recorded 1.06 of rain within a few hours.
Report of roadway flooding on I-10 just west of Bob Hope Drive.
Mesonet station 4 miles ESE Perris recorded a 76 mph gust associated with thunderstorm outflow. Likely a microburst.
Rocks and debris reported along Sage Rd at Highway 79 and along Sage Rd between Lewis Rd and Cottonwood School.
Report of roadway flooding on Highway 86 just south of 66th Avenue in Mecca.
Report of a tree down blocking the Emerett Ln in Perris. Nearby SCE Orange Avenue station reported a peak wind gust of 41 mph at 420 PM.
Sand across Highway 18 between Cushenbury and Lucerne Valley due to heavy rain.
Road closed for flooding on Highway 247 in multiple areas including near Charro Rd with rushing water and rock debris.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2025Every state in 2025This day in weather historyWarnings in California, August 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1292964, 1292690, 1292972, 1292971, 1292697, 1292961, 1292691, 1292977, 1292692, 1292978, 1293022, 1292693, 1293035, 1293040, 1292975, 1293006, 1292995.