The National Weather Service has placed all of Puerto Rico and the U.S. Virgin Islands under a Heat Advisory from 11 a.m. through 4 p.m. AST today, warning of elevated heat illness risk across both territories during peak afternoon hours.
The advisory covers a wide geographic footprint. In Puerto Rico, affected zones include San Juan and its vicinity, the northeast, southeast, north-central interior, the Ponce corridor, the northwest, the Mayaguez area, and the southwest coast. The island municipalities of Culebra and Vieques are also included. On the U.S. Virgin Islands side, the advisory extends to St. Thomas, St. John, and adjacent islands, as well as St. Croix.
The National Weather Service said current heat and humidity levels will affect most individuals sensitive to heat — particularly those without effective cooling or adequate hydration. The agency also flagged potential impacts in some health systems and heat-sensitive industries during the advisory window.
San Juan weather and Ponce weather — Puerto Rico’s two most populous metropolitan areas — sit at the center of the advisory zone. Urban surfaces, dense development, and limited overnight cooling in city neighborhoods can compound heat exposure during afternoon hours.
The five-hour advisory window is designed to capture the period of peak surface heating. Heat illness can develop quickly in high-humidity environments, particularly among people who are outdoors for extended periods, elderly individuals, or workers in non-air-conditioned settings. The National Weather Service advises residents to drink plenty of fluids, stay in air-conditioned rooms, avoid direct sun exposure, and check on neighbors and relatives who may not have reliable access to cooling.
Puerto Rico and the Virgin Islands experience high baseline temperatures and humidity year-round, but Heat Advisory conditions signify a threshold above that norm — one at which physiological stress becomes a documented medical concern for sensitive populations. People with chronic cardiovascular or respiratory conditions face elevated risk, as do outdoor laborers who cannot easily seek shelter during afternoon hours.
No storm system is driving the heat event, and no extension of the advisory had been announced as of this writing. The National Weather Service will post updated guidance if conditions warrant further action after 4 p.m. AST.