The National Weather Service (NWS) office in San Juan issued a flash flood warning for Caguas on Wednesday, in effect until 4:45 PM, and a flood advisory for six towns in western and southwestern Puerto Rico, in effect until 6:15 PM. The Caguas advisory, which included a request to activate the Emergency Alert System, was issued after Doppler radar detected thunderstorms producing heavy rain over the town at 1:43 PM. Between 1 and 2 inches of rain had already accumulated there, and the NWS projected 1 to 3 additional inches, which could bring totals to 5 inches in the hardest-hit sectors. The agency warned that flash flooding could already be developing, citing streams, urban areas, roads, overpasses and poorly drained low-lying areas as vulnerable, and noted that low-water road crossings are especially dangerous in mountainous terrain.
The western warning covers Hormigueros, Sabana Grande and San Germán, plus northern Cabo Rojo and Yauco and southern Mayagüez. A bulletin issued at 3:09 PM reported up to 2 inches already fallen there, with up to 1 more inch expected, for possible totals of 3 inches. The NWS urged drivers not to cross flooded roads, use alternate routes, and note that most flood-related deaths occur in vehicles.