By Reginald Stanley. Posted January 1, 2024, 9:12 PM.

On average, December is typically one of the coldest months of the year across much of Southern California - however, in 2023, December was dominated mainly by balmy temperatures and few storms.

Across the vast majority of active WeatherCurrents stations, December 2023 ended as the second-warmest December in their historical records, behind an even warmer and drier December the region experienced in 2017. Only in Temecula did 2023 tie with 2017 for the warmest December on record. The first half of the month featured near-constant Santa Ana Wind episodes and warm temperatures, before rainy conditions finally arrived during the second half of the month. These storms, however, were few in number and all had weakened upon entering southwestern California, resulting in relatively scant precipitation and below average totals for the month of December. Parts of the state from Ventura and Santa Barbara counties northwards benefited much more from these storms.

A persistent high pressure ridge over the Rocky Mountains has been largely responsible for the weakening and splitting of incoming storms from the Pacific Ocean. In addition, most of these storms have been cutoff lows (also called closed lows) with behavior that is often erratic and difficult to predict, or systems with limited moisture. Several colder storms are set to impact the region later this week, before a potential cold wave digs down the west coast of the United States from the Arctic next week. Updated maps from the Climate Prediction Center website indicate above-average chances of below normal temperatures across Southern California for the month of January, as well as increased chances of above-average precipitation.