San Francisco Bay Area Records Driest Start to December in Decades as Storms Approach

Driest Start to December Recorded Across Bay Area

Most of the San Francisco Bay Area has not recorded any measurable rainfall so far this December, resulting in the driest start to the month in decades for numerous locations across the region.

Historic Dry Conditions by City

In Monterey, the current beginning of December is the driest since 1976. Half Moon Bay is experiencing its driest early December period since 1979. San Francisco, Oakland, Napa, Santa Rosa, and Salinas are all seeing their driest start to December since 1989.

Livermore and Redwood City have not had an early December this dry since 2011. San Jose, Fairfield, Petaluma, and Watsonville are experiencing their driest early December conditions since 2017.

Weather Pattern Behind the Dry Spell

A high-pressure system has dominated the weather pattern over California for the past two weeks. This system has maintained dry conditions across the Bay Area and redirected atmospheric moisture toward the Pacific Northwest, where it has produced historic flooding.

The high-pressure system has also trapped fog and pollution, including emissions from wood-burning heaters, near the surface. As a result, air quality in the region has been poor and fog has persisted.

Rain Forecast and Changing Conditions

Forecasters report that the dry pattern is expected to change as multiple storm systems move toward the Bay Area this week and continue through the end of the month. These incoming systems are expected to end the stagnant weather pattern.

The first chance of rain in the Bay Area is forecast to arrive late Tuesday into early Wednesday morning, with total rainfall accumulations predicted to be less than 0.25 inches.

A stronger storm system, accompanied by an atmospheric river, is forecast as of Sunday to begin affecting the Bay Area in the late Friday timeframe and continue into the weekend before Christmas. The anticipated shift to wetter conditions is expected to improve air quality and allow the persistent fog to lift.