FEMA flood map notices

Flood map changes in San Mateo County, California

FEMA has published 6 flood hazard notices covering San Mateo County, California since November 2023. The most recent, map revision flood hazard determinations, was published Jul 9, 2026.

Notices for San Mateo County

Jul 9, 2026Map revisionChanges in Flood Hazard DeterminationsAlso covers 13 other counties
Dec 8, 2025Map revisionChanges in Flood Hazard DeterminationsAlso covers 25 other counties
Jun 11, 2025Map revisionChanges in Flood Hazard DeterminationsAlso covers 31 other counties
Jan 8, 2025Map revisionChanges in Flood Hazard DeterminationsAlso covers 9 other counties
Oct 22, 2024Map revisionChanges in Flood Hazard DeterminationsAlso covers 13 other counties
Aug 1, 2024Map revisionChanges in Flood Hazard DeterminationsAlso covers 28 other counties

Also covered by these notices

FEMA often studies whole watersheds, so one notice can span several counties.

What these notices mean

Proposed: FEMA has new draft flood maps. This starts a 90-day window when owners can appeal with technical data. It's the best time to act.
Final: Appeals are resolved. The new maps usually take effect about six months later, when lenders start applying the new zones.
Map revision: A Letter of Map Revision changes one stretch of the map, often after a levee, channel project or new survey.

Notices are organized by county and community, so a notice for your county doesn't mean your property is changing zones. What flood zones mean