Sep 18, 2025
The combination of an upper-level low off the CA coast and the remnants of Tropical Cyclone Mario resulted in a significant moisture increase with PWATs rising to 1.5 on the 17th and upwards of 1.8-2.0 on the 18th. Thunderstorms on the 17th were concentrated mainly across the higher terrain areas of southeast CA, mainly across the Chocolate Mountains, while on the 18th, the activity was more widespread as upper-level forcing from the combination of the upper-level low and the remnants of Tropica
Source: NOAA National Weather Service Storm Events Database (event 1293016). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Riverside County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.