The National Weather Service (NWS) office in San Juan says Puerto Rico will see relatively calm conditions through Friday, with rain expected to increase over the weekend. A drier air mass moving in from the east will gradually limit rain activity Thursday night and Friday, though passing showers could fall overnight in eastern Puerto Rico and the US Virgin Islands.
On Friday, daytime heating will favor isolated to scattered showers in the west and northwest of the island. Flood risk stays limited, but heavier rain could pool water on roads and cause minor urban flooding in areas with poor drainage. Temperatures will remain above normal, so the agency recommends staying hydrated and taking precautions against heat exposure.
Conditions could shift starting Saturday, when moisture increases as a trough deepens over the western Caribbean. Showers and isolated thunderstorms could develop Saturday afternoon in the interior and west, with rain potential rising late in the day and extending into Sunday. The GFS and ECMWF weather models project precipitable water values near or above two inches, which could bring moderate to locally heavy rain and raise the risk of urban and stream flooding where showers persist, plus lightning if thunderstorms develop.
Forecasters have moderate confidence in the wetter trend but say there is uncertainty about where the heaviest rain would fall and how strong it would be. Friday and Saturday morning are the best windows for outdoor activities.