By Reginald Stanley. Posted September 8, 2026, 9:26 PM.

Triple-digit heat has returned to the region Tuesday, prompting the National Weather Service to issue an Extreme Heat Warning for the coasts, valleys and low desert until 8 PM Wednesday, as well as a Heat Advisory until 8 PM Thursday.

Thunderstorms previously forecasted to impact the mountains on Tuesday, along with southeasterly flow, helped produce a large thunderstorm over Agua Tibia Mountain and Palomar Mountain Tuesday afternoon. As the thunderstorm grew and rapidly intensified, rain began to spill over into Temecula to the north, as well as Anza to the east. This prompted the National Weather Service to briefly issue a Severe Thunderstorm Warning for Temecula and Murrieta, however the thunderstorm weakened significantly just north of Temecula Tuesday evening. Thunderstorms had also formed over the San Diego County mountains. In addition, a large grouping of thunderstorms off the coast of Ventura County managed to bring rain to Simi Valley, although these storms had weakened upon moving ashore. Measurable precipitation was recorded at four WeatherCurrents stations Tuesday - in Simi Valley, Pinon Hills, Murrieta, and Anza.

Building high pressure over Southern California over the next several days is expected to limit further thunderstorm development in the region, with tropical moisture being pushed further north Wednesday and Thursday. Temperatures are forecast to begin cooling once again this weekend.

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