textproduct: San Juan

KEY MESSAGES

Issued at 142 AM AST Wed Aug 5 2026

- Warm-to-hot conditions will continue to be the main threat, particularly across urban and low-lying areas of the islands. A Heat Advisory will be in effect from 10 AM through 5 PM AST across Puerto Rico and the US Virgin Islands.

- Periods of brief showers will continue to filter across the islands today, leading to ponding of water on roadways and in poorly drained.

- A more stable weather pattern is forecast for the next few days, with limited shower activity and an increase of Saharan Dust concentrations late this weekend.

Short Term(Today through Friday)

Issued at 142 AM AST Wed Aug 5 2026

Overnight pockets of showers prevailed over the waters and some filter over the eastern half of Puerto Rico and the US Virgin Islands. Regardless, accumulations remained low. Temperatures remained in the upper 70s to low 80s in the coastal areas, while across the mountainous areas in the 70s. winds remain low and variable.

Today will be a transitional weather day across the local islands as a weak moisture band moving across the area will support periods of passing showers through the morning, mainly over the windward sectors. By afternoon, daytime heating and local effects will shift shower and thunderstorm development toward the interior and western Puerto Rico, where locally heavy rainfall may lead to ponding of water in poor drainage areas. Winds will shift from northeasterly to easterly and eventually east-southeasterly.

By late Wednesday into Thursday, a drier and more stable air mass will gradually filter across the region. As moisture decreases and subsidence strengthens aloft, shower coverage and intensity will diminish, with the driest conditions expected from Thursday into Friday. Rainfall during this period will be largely limited to isolated trade wind showers during the overnight and morning hours, followed by isolated afternoon convection over the interior and western Puerto Rico driven primarily by local effects.

As the rainfall threat decreases, heat becomes the primary weather hazard. East-southeasterly winds will promote above-normal temperatures, especially across the northern, southern, and eastern coastal plains of Puerto Rico, as well as the U.S. Virgin Islands. Combined with increasing sunshine and limited cloud cover, heat index values are expected to reach hazardous levels each afternoon. Therefore, a Heat Advisories was issued for today. However, warning criteria is possible from Thursday into Friday.

Long Term(Saturday through Wednesday)

Issued at 142 AM AST Wed Aug 5 2026

A drying trend is expected for most of the long-term period as a strengthening, broad surface high-pressure system extending across the western and central Atlantic dominates local weather conditions. Under this pattern, an east-to-southeast wind flow will prevail through Monday, turning east-northeasterly from Tuesday onward.

An upper-level low-pressure system moving across the region from Saturday into Monday will provide slight instability aloft, reflected in cooler 500 mb temperatures dropping to between -6C and -7C. However, despite this atmospheric setup, overall drier conditions are expected, though patches of low-level moisture carried by the trade winds will move across the region from time to time. During this period passing showers will affect eastern Puerto Rico and the U.S. Virgin Islands during the morning hours. Followed in the afternoon, available moisture combined with diurnal heating and local sea-breeze effects could trigger localized convective activity across central and western Puerto Rico.

Warmer-than-normal temperatures will persist throughout the forecast period. Model guidance indicates 925 mb temperatures near two standard deviations above normal for this time of year, which, combined with lingering moisture, could result in Heat Advisories or Extreme Heat Warnings, particularly on Monday.

AVIATION

(06Z TAFS) Issued at 142 AM AST Wed Aug 5 2026

VFR conditions across all TAF sites. VCSH will continue to prevail across most sites. SHRA/VCTS can develop over west PR, possibly reducing visibilities and ceilings at TJBQ from 05/17Z trough 05/23Z. Winds will gradually transition from NE to the E from 11Z onwards.

MARINE

Issued at 142 AM AST Wed Aug 5 2026

Marine conditions will remain generally favorable for small craft, although locally choppy conditions are possible from Friday into the weekend as winds and seas increase. Afternoon thunderstorms may produce locally hazardous conditions near western Puerto Rico today. Moderate Saharan dust will return Friday, followed by a tropical wave and increased shower activity this weekend.

BEACH FORECAST

Issued at 142 AM AST Wed Aug 5 2026

A low risk of life-threatening rip currents is expected today through most of Thursday. A moderate risk will develop late Thursday and expand across many exposed beaches of northern and eastern Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands from Friday through the weekend.

Elevated to locally significant heat risks are expected each day, with the highest risks today, Thursday, and again Monday. Afternoon thunderstorms may produce lightning, gusty winds, brief heavy rain, and reduced visibility, particularly across western Puerto Rico. Moderate Saharan dust is expected to return Friday.

FIRE WEATHER

Issued at 142 AM AST Wed Aug 5 2026

Critically fuels continue across the islands, particularly across the southern portions of Puerto Rico and St. Croix in the U.S. Virgin Islands. However, periods of showers associated with surface disturbance will continue to increase moisture across the area and winds will remain below 18 mph today. Regardless, low fire weather risk is anticipated today.

From late Wednesday into the end of the workweek, stable weather pattern and strengthening winds are likely in the next few days, and combined with very dry fuels, the fire danger will likely increase. Residents and visitors are encouraged to continue to monitor the fire weather conditions and avoid outdoor burning.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for PRZ001>005-007-008-010>013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for VIZ001-002.

AM...None.