https://www.mercurynews.com/2023/01/03/bay-area-flooding-how-to-sign-up-for-alerts-in-your-neighborhood/

All Bay Area counties are under a flood watch from late Tuesday to Thursday afternoon.

For “considerable or catastrophic” hazards, emergency alerts will be sent to all enabled mobile phones in the area. To monitor lesser risk, residents are advised to sign up for county alert systems and to monitor agencies’ social media.