Guam, Northern Mariana Islands Unknown Hydrologic Outlook | Effective 08/23/2026 01:44

ESFGUM This Hydrologic Outlook is for Guam, Rota, Tinian, and Saipan. A reinvigorated monsoon trough with a potential embedded tropical disturbance will likely develop in the area and bring periods of heavy rainfall to the Marianas starting midweek. Between Wednesday and Friday, early ensemble guidance suggests 4 to 6 inches with a low probability of up to 10 inches for Guam and Rota, and 3 to 5 inches with a low probability of up to 8 inches for Saipan and Tinian. Heavy showers will moisten soils throughout the event and increase potential for mudslides. Residents of the Marianas need to closely monitor this developing situation as flood watches, advisories and flash flood warnings could be issued later. If living near streams and rivers, prepare to move items away from stream and river banks. Make sure storm drains nearby are not clogged, especially If living at low-lying areas.