By Reginald Stanley. Posted October 20, 2023, 1:49 AM.

The strong, persistent upper level high pressure ridge that has brought widespread near-record heat to Southern California for the past week is forecast to weaken over this weekend, allowing for cooler onshore flow to return and even bring a chance of showers to the region on Monday.

Triple-digit heat was observed at many WeatherCurrents stations in recent days, particularly in Lake Elsinore, San Jacinto, and Perris. Lake Elsinore recorded a high temperature of 104 degrees on October 19. Other locations saw temperatures in the upper 90s during this time as well. October's abnormal, persistent warmth thus far has resulted in monthly average temperatures significantly above normal, four-to-five degrees above average - in Murrieta, October is so far almost a full degree warmer than September has been. In Hemet, this October is almost two degrees warmer than September; while in Riverside (Orangecrest) this month is just over two degrees warmer. Most other WeatherCurrents stations are observing October monthly average temperatures very close to that of September. These averages are likely to come down somewhat by the end of the month.

A cutoff low pressure system will bring cooling, a deep marine layer and a slight chance of showers to the region early next week, particularly on Monday. Precipitation amounts from this system are currently expected to be light, if any. There is uncertainty among computer forecast models regarding the timing of the exit of the cutoff low, however current guidance suggests Tuesday or Wednesday. Following a brief period of mild warming mid-week, another low pressure system is predicted to bring further cooling to the region late in the week.