Guam, Northern Mariana Islands Coastal Flood Warning | Effective 04/12/2026 22:54

* WHAT...For the High Surf Warning, dangerously large breaking waves of 12 to 16 feet for Guam and 15 to 25 ft for Rota, Tinian and Saipan. For the Coastal Flood Watch, significant coastal flooding 1 to 3 ft for Guam, and 4 to 8 ft for Rota, Tinian, and Saipan. * WHERE...North, east and south facing reefs of the Marianas. For the Coastal Flood Watch, north, east, and south facing shorelines. * WHEN...For the High Surf Warning, until 6 PM ChST Thursday. For the Coastal Flood Watch, through Wednesday afternoon. * IMPACTS...Numerous roads may be closed. Low lying property including homes, businesses, and some critical infrastructure may be inundated. Some shoreline erosion may occur. Breaking waves can sweep people off jetties and docks, and into dangerous seas. Life- threatening swimming conditions and significant beach erosion can be expected. * ADDITIONAL DETAILS...As STY Sinlaku moves towards the Marianas swell and surf will continue to build. This will maintain dangerous surf and coastal inundation, especially as STY Sinlaku begins to move through the Marianas on Tuesday. Inundation has already been reported at Inarajan Pools.