textproduct: San Juan

KEY MESSAGES

Updated at 227 PM AST Sat May 30 2026

* Saharan dust will continue to promote hazy skies and reduced visibilities through early next week, increasing in concentrations late Sunday through Tuesday.

* Sensitive groups, including people with respiratory conditions, may experience discomfort and should follow medical recommendations due to this saharan dust.

* A tropical wave will bring a brief surge in moisture content tomorrow, Sunday, promoting an increase in passing and scattered showers.

* Hot conditions are expected through early next week, particularly along the lower elevations and urban areas. Heat Advisories could be issued later on.

Short Term(This evening through Monday)

Issued at 227 PM AST Sat May 30 2026

Mostly tranquil conditions prevailed during the morning hours, with very limited shower activity and moderate SAL concentrations across the region. CACWOP/ASOS/AWOS stations across the islands have reported maximum temperatures so far between the mid 80s and low 90s across urban and coastal areas of the islands, and higher elevations remained in the mid 70s and low 80s. Additionally, stations across northern and western portions of Puerto Rico and St. Croix in the U.S. Virgin Islands have reported heat indexes exceeding 100 degrees Fahrenheit. Winds have strengthened this morning, with some stations reporting maximum wind gusts up to 25 and 26 mph. The 12z RAOB reported PWAT values around 1.53 inches, typical for this time of the year, though theres a drier slot in the mid levels (RH around 39%). Additionally, the sounding shows slightly cooler than normal mid-level temperatures (-8.5 degrees Celsius), due to the proximity of an upper-level trough. Although HI-RES models suggest the development of showers across northwestern portions of Puerto Rico, rainfall accumulations should remain limited, with mainly localized ponding of water over roadways and poorly drained areas.

The short-term forecast remains on track. A broad surface high pressure over the Central Atlantic should maintain east to east- southeast winds through most of the period. Satellite-derived products show an area of high moisture content associated with a tropical wave east of the Leeward Islands, with PWAT values of 1.8- 2.0 inches. This tropical wave should move across the Caribbean basin, with moisture content reaching the CWA on Sunday morning. Although the main convection activity should remain well south of the CWA, the deterministic guidance of both GFS and ECMWF suggests this gradual increase in moisture content across the region, particularly in the 850-700 mb layer (up to 70 - 80 %). In the mid to upper-level, the proximity of an upper-level trough should maintain cooler than normal mid-level temperatures (500 mb temperatures between -8 and -10 degrees Celsius), enhancing deep convection. The most likely scenario remains, with showers moving over windward sections of the islands Sunday morning, though rainfall accumulations should remain limited. By midday into the afternoon, due to the combination of daytime heating, local effects, and seabreeze convergence, convection activity should concentrate over portions of interior and western/northwestern Puerto Rico. These rainfall accumulations should enhance flooding potential, resulting in ponding of water that may cause urban and small stream flooding over the aforementioned areas. By Sunday evening, a broad and dense SAL layer should filter into the region, persisting through Monday. As both the tropical wave and the trough continue to move away from the region, moisture content will diminish and drop to below normal for this time of the year. Although shower activity can still be expected, it should remain limited, with low flood and lightning potential on Monday.

Warmer-to-hotter conditions are expected in the short-term forecast, and with the available moisture, may combine and increase heat risk. Hence, expect heat indices to exceed 100 degrees Fahrenheit, particularly over urban and coastal areas of Puerto Rico and the U.S. Virgin Islands. Residents and visitors must exercise caution, as these levels may impact most individuals sensitive to heat and/or without adequate hydration. A Heat Advisory may be issued if required.

Long Term(Tuesday through next Friday)

Issued at 307 AM AST Sat May 30 2026

The Saharan Air Layer (SAL) will linger across the region on Tuesday as it gradually shifts westward away from Puerto Rico and the U.S. Virgin Islands. Therefore, hazy skies, reduced visibilities at times, and limited shower activity are expected to persist through much of the day. However, model guidance continues to indicate the arrival of a low- to mid-level wind surge, particularly between 850 and 700 mb, beginning on Tuesday and persisting into Wednesday. This feature should result in breezier conditions across the local islands while also promoting the advection of clouds and a few passing showers, especially from late Tuesday night into early Wednesday.

Associated with this wind surge, guidance also suggests the arrival of a weak vorticity maximum at similar levels, reaching its greatest influence on Wednesday as a weak easterly disturbance moves across the northeastern Caribbean. At the same time, a surge of moisture is forecast to reach the region, allowing precipitable water values to recover to near-climatological levels for early June. This increase in moisture should support a more typical seasonal weather pattern, consisting of periods of passing showers affecting the U.S. Virgin Islands and eastern Puerto Rico during the overnight and morning hours, followed by afternoon convection across interior and western Puerto Rico. Low-level convergence may also enhance shower activity at times across the U.S. Virgin Islands and eastern Puerto Rico.

Despite increased moisture and low-level forcing, the overall environment does not appear favorable for organized or widespread convective development. Mid-level temperatures near 500 mb remain relatively warm, which should limit instability and vertical growth. In addition, drier air aloft is expected to persist through much of the period, favoring subsidence and further restricting deep convection. As a result, rainfall activity should remain generally scattered and locally driven, with no significant signals for prolonged or organized thunderstorm activity.

Low-level temperatures are forecast to return to more typical early June levels after the departure of the Saharan dust intrusion. Therefore, the overall weather pattern through Friday is expected to remain relatively tranquil, characterized by breezy conditions on Tuesday and Wednesday, near-normal moisture levels from Wednesday onward, occasional passing showers across windward areas, and localized afternoon convection over portions of interior and western Puerto Rico.

By Saturday, forecast confidence begins to decrease. Global model guidance suggests a transition toward a somewhat more unsettled weather pattern associated with the possible approach of a tropical wave and the proximity of an upper-level feature. Should these features materialize as currently indicated, moisture availability and instability could increase across the region, leading to greater coverage of showers and thunderstorms. However, given that these features remain near the end of the forecast period, considerable uncertainty persists regarding their timing, intensity, and overall influence on local weather conditions. Therefore, future forecast updates will likely refine the details of this potential pattern change as confidence increases.

AVIATION

(18Z TAFS) Issued at 227 PM AST Sat May 30 2026

Mainly VFR conditions across the terminals. Afternoon, locally induced -TSRA/SHRA can develop over interior to W-NW PR through around 30/22Z, this can affect TJBQ and can result in temporary MVFR conds. Over windward sectors, occasional limited VCSH are possible. HZ due to saharan dust will also continue thru the period, with reduced VIS (btw 6 to 8 SM) possible. ESE winds at 10 to 16 kt, with higher gusts and sea breeze variations, decreasing after 30/23z.

MARINE

Issued at 227 PM AST Sat May 30 2026

A surface high pressure over the central Atlantic will continue to promote generally moderate to locally fresh east to east-southeast winds for the rest of the weekend into early next workweek across the islands. Seas will remain at 3 to 4 feet, with occasionally higher seas up to 5 feet or higher. Mariners should remain weather alert as afternoon showers and thunderstorms could develop and move over the coastal waters of northwestern Puerto Rico. Moisture associated with an approaching tropical wave will likely enhance shower and thunderstorm activity across the regional waters, tomorrow Sunday. Moderate to high concentrations of Saharan dust will persist for the rest of the weekend, increasing by Sunday afternoon into Tuesday, resulting in hazy skies, reduced visibility, and poor air quality.

BEACH FORECAST

Issued at 227 PM AST Sat May 30 2026

A low risk of rip currents will continue through Monday afternoon. However, life-threatening rip currents often occur near groins, jetties, reefs, and piers. The risk is forecast to increase to moderate by Monday evening and continue through the rest of the week.

Moderate to high concentrations of Saharan dust will persist this weekend, with higher particle concentrations reaching the islands by Sunday afternoon into Tuesday, resulting in hazy skies, reduced visibility, and poor air quality. Beachgoers are highly encouraged to stay weather alert as showers and isolated thunderstorms could develop in the afternoon and move near coastal areas of western and northwestern Puerto Rico, bringing gusty winds and lightning.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...None.