textproduct: San Juan

KEY MESSAGES

Updated at 226 PM AST Wed Aug 26 2026

* Warmer temperatures will continue across the islands, with an elevated to locally significant heat risks throughout the remainder of the week.

* As the drier airmass and Saharan dust layer move from the local area, showers and isolated thunderstorms are expected on Thursday afternoon, increasing the flooding and lightning threat.

* The potential for life- threatening rip currents will increase to moderate from this evening onward, especially along most exposed beaches of Puerto Rico and the US Virgin Islands.

* A weak tropical wave will move quickly across the region late Friday night into Saturday morning, increasing showers and thunderstorms, followed by brief drier conditions.

* The National Hurricane Center continues to monitor AL96, with a medium formation chance of development, though uncertainty remains high regarding impacts, if any, across the islands.

Short Term(This evening through Friday)

Issued at 226 PM AST Wed Aug 26 2026

Hazy skies and generally fair weather conditions prevailed across the islands during the morning hours as moderate concentrations of Saharan dust remained across the region. Shower activity was limited, with only a few passing showers noted over the local waters. Meanwhile, warm temperatures combined with sufficient low- level moisture will continue to result in elevated to locally significant heat risks, particularly across urban and coastal areas. Therefore, the Extreme Heat Warning and Heat Advisory remain in effect through 5 PM AST.

For this afternoon, precipitable water values are expected to remain near seasonal levels, generally between 1.6 and 1.7 inches. However, relatively dry air in the mid-levels, consistent with the lingering Saharan air layer, should limit the overall coverage of convection. Nevertheless, sufficient low-level moisture combined with strong daytime heating, sea-breeze convergence, and local effects will support isolated to scattered showers, mainly across the interior and western/southwestern portions of Puerto Rico. Locally heavy rainfall could result in ponding of water on roads and in poorly drained areas, with a limited flooding risk where the heaviest rainfall occurs. Moderate Saharan dust concentrations will also maintain hazy skies through this evening.

A gradual increase in moisture is expected tonight into Thursday as a moisture surge moves across the region. Precipitable water values will increase to around 1.8-1.9 inches, while low- to mid-level relative humidity increases as the Saharan air layer gradually erodes. Therefore, passing showers are expected to increase across the local waters and windward portions of the islands during the overnight and morning hours. By Thursday afternoon, the combination of deeper moisture, daytime heating, and local effects could favor a round of showers and thunderstorms across the interior and western portions of Puerto Rico. Although lapse rates aloft are expected to become somewhat less favorable, the deeper moisture profile should support locally heavy rainfall with the strongest activity. A limited to elevated flooding risk will persist, but widespread flooding is not anticipated.

A noticeable drying trend is then expected Thursday night into Friday as increasing subsidence develops ahead of this weekend's tropical wave. Model guidance indicates precipitable water values falling below seasonal levels, accompanied by a pronounced decrease in low- and mid-level relative humidity and more stable conditions aloft. These conditions should limit shower and thunderstorm activity through much of Friday. Nevertheless, sufficient low-level moisture, daytime heating, and local effects may still support isolated afternoon convection, mostly shallow, mainly across western Puerto Rico. Additionally, low-level winds are expected to strengthen somewhat through the latter part of the short-term period, maintaining breezy conditions, particularly along coastal areas.

Late Friday night, moisture will increase rapidly as a weak tropical wave approaches from the east. Precipitable water values are forecast to increase to around 2.0-2.2 inches, accompanied by a substantial increase in low- and mid-level relative humidity. This could increase the frequency of shower activity across windward coastal areas during Friday night period.

Long Term(Saturday through next Tuesday)

Issued at 303 AM AST Wed Aug 26 2026

A brief, weak tropical wave will move quickly across the region between late Friday night and Saturday morning, temporarily increasing moisture and supporting passing showers and isolated thunderstorms across Puerto Rico and the U.S. Virgin Islands. A rapid drying trend is expected behind the wave, as a dominant surface high settles over the central Atlantic and a mid-level ridge builds across the region. Drier and more stable conditions should become established by Sunday, with precipitable water values falling below climatological normals to around 1.25 inches through Monday morning.

Uncertainty increases during the second half of the forecast period, as local conditions will depend on the track and future intensity of tropical wave AL96, currently south-southwest of the Cabo Verde Islands. Latest guidance still suggests the system will pass northeast of the region between Monday afternoon and Wednesday. Nevertheless, its evolution will continue to be monitored for potential indirect impacts. Given the uncertainty, residents and local interests should monitor subsequent forecasts as AL96 moves across the Atlantic.

Meanwhile, seasonal to above-seasonal 925-mb temperatures will persist throughout the period, resulting in elevated to possibly significant heat risks each day.

AVIATION

(18Z TAFS) Issued at 226 PM AST Wed Aug 26 2026

Mainly VFR conds expected across all terminals. Saharan dust will maintain HZ with VIS generally above 6SM. Increasing moisture tonight will favor more frequent SHRA after 26/22Z, particularly across windward PR/USVI terminals, but impacts should remain minimal. SHRA/TSRA development is expected Thu aft, with VCTS at TJPS/TJBQ after 27/17Z. E-ESE winds at 10-15 kt with sea breeze variations, becoming lighter overnight.

MARINE

Issued at 226 PM AST Wed Aug 26 2026

Surface high pressure across the central Atlantic will continue to support a moderate east-to-east-northeasterly steering flow for the rest of today, becoming more east-to-east-southeast tomorrow onward. Saharan dust concentrations will gradually decrease late tonight into Thursday, followed by shower and thunderstorm activity across the local Atlantic waters and passages. A weak long-period northeasterly swell remains on forecast to arrive and spread across the regional waters by tomorrow, Thursday morning. Showers and isolated thunderstorms associated with a tropical wave are forecast to stay mainly over the local Caribbean waters and passages by late Friday night into Saturday. Winds may briefly become moderate to locally fresh as the tropical wave moves across the area, with seas between 3 and 5 feet, occasionally 6 feet; small craft must exercise caution.

BEACH FORECAST

Issued at 226 PM AST Wed Aug 26 2026

The risk of rip currents is expected to increase tonight, becoming moderate along northern and eastern-exposed beaches of Puerto Rico and the U.S. Virgin Islands. Beachgoers must exercise caution, as life-threatening rip currents are possible along the surf zone. A weak long-period northeasterly swell remains on forecast to arrive and spread across the regional waters by tomorrow, Thursday, though the latest guidance shows a minimal increase in seas, with breaking waves between 3 and 5 feet. Therefore, the risk will remain moderate for the next few days. Aside from rip currents, beachgoers must remain weather alert as showers and isolated thunderstorms can be expected each afternoon across western coastal areas of Puerto Rico. Isolated thunderstorms could produce gusty winds and lightning, and beachgoers should seek shelter whenever they hear thunder.

FIRE WEATHER

Issued at 226 PM AST Wed Aug 26 2026

Fire weather conditions became more favorable for rapid fire spread late this morning, prompting the issuance of a Fire Danger Statement (RFD) through 5 PM AST for portions of Puerto Rico and the U.S. Virgin Islands. Low relative humidity values, sustained easterly winds between 10 and 15 mph with higher gusts, and dry fuels will continue to support elevated fire weather conditions through this afternoon. The greatest concern remains across southern and southwestern Puerto Rico, where fuels remain exceptionally dry. Increasing moisture later today and tonight should promote better humidity recovery and gradually reduce the fire weather threat.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Extreme Heat Warning until 5 PM AST this afternoon for PRZ001>005-007-008-010-011.

Heat Advisory until 5 PM AST this afternoon for PRZ012-013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...None.