The National Weather Service (NWS) in San Juan issued a heat advisory for Puerto Rico valid Tuesday from 10:00 a.m. to 5:00 p.m., covering coastal, urban and lower-elevation areas, including Vieques and Culebra, as well as the U.S. Virgin Islands. Forecasters attributed the danger to a combination of high clouds, moderate to elevated Saharan dust concentrations, and dry air in the mid-atmosphere, which will keep conditions hot, hazy and mostly dry.
Overnight lows in many coastal municipalities and some inland areas ranged between 80 and 82 degrees Fahrenheit, limiting nighttime cooling and raising heat index values. East winds will bring passing showers to windward areas, while western Puerto Rico will see only isolated afternoon rain; Saharan dust and dry air will limit significant rainfall and worsen air quality. Conditions are expected to shift Tuesday night as a fast-moving tropical wave crosses the region, increasing humidity by Wednesday and bringing scattered showers and isolated thunderstorms, along with possible road flooding, minor urban and small-stream flooding, and frequent lightning in stronger storms.
However, the NWS said the relief will be short-lived, with a much drier air mass and renewed Saharan dust expected to arrive between Wednesday night and Thursday.