By Reginald Stanley. Posted October 5, 2021, 4:18 PM.

A cutoff low off the coast of northern Baja California moved northeast over the region Monday and Tuesday, producing significant thunderstorms across most of Southern California Monday evening, with some rain continuing into Tuesday morning.

Increasingly cloudy skies were observed throughout Monday as instability gradually increased over the day, finally leading to several waves of intense thunderstorms travelling over the region late Monday evening. The entire region was treated to spectacular lightning shows and loud thunder throughout the evening, and many locations reported brief bouts of small hail and sudden high winds. Many communities inland received rainfall before midnight, although much of the rain fell in the early morning hours of Tuesday, before giving way to partly cloudy skies later Tuesday morning. Some residual moisture continued to linger in the mountains as of Tuesday afternoon.

Most active WeatherCurrents stations recorded measurable rainfall, except for WeatherCurrents' station in Pinon Hills. Storm totals ranged from 0.08 inches in Riverside (Orangecrest) to as high as 0.74 inches in Fallbrook., with the majority of WeatherCurrents stations recording between 0.10 and 0.50 inches. Thunderstorms were particularly severe over Fallbrook, De Luz, Anza and parts of the Temecula Valley, where higher totals were concentrated. In Temecula Valley's Wine Country, 0.31 was reported (courtesy of Jim Sappington) while in East Highland, a total of 0.26 inches was reported (courtesy of Peter Michas). Totals were generally less than 0.20 inches in other parts of the Inland Empire, as well as in Simi Valley northwest of Los Angeles. Totals from Beaumont (Cherry Valley) and Riverside (Presidential Park) were not included due to prolonged station outages there. The thunderstorms followed a moderately active monsoon the region witnessed over the summer, in contrast to the much quieter summers of 2019 and 2020.

Another low pressure trough is expected to bring rain chances to the region Thursday night and Friday, with additional rain chances possible once again next week.

Here are the rain totals for the WeatherCurrents network and associates: