textproduct: San Juan

KEY MESSAGES

Updated at 357 AM AST Sat Jun 6 2026

* Cloudiness along most of western Puerto Rico will remain due to an induce surface trough well east over the Hispaniola spreading into our area.

* A warming trend is forecast from today through Sunday as southeast winds persist across the region and abundant sunshine prevails during the daytime hours. Heat indices are expected to reach up to 108 degrees across urban and coastal areas of Puerto Rico. On Sunday, heat indices between 105 and 111 degrees are forecast to be more widespread.

* A pulse of Saharan dust is forecast to arrive late tonight and persist through Monday. This dust intrusion will coincide with an increase in low-level moisture associated with an approaching tropical wave. As a result, warm temperature sensation and hazy skies are expected across the region on Sunday.

* There is a low to moderate risk of rip currents across the exposed beaches of Puerto Rico and the U.S. Virgin Islands.

Short Term(Today through Monday)

Issued at 357 AM AST Sat Jun 6 2026

Variable weather conditions prevailed overnight across the local islands, with mostly cloudy skies observed across most of the west side of the CWA due to an induced surface trough located west of the area over the Hispaniola. The TDWR radar detected isolated shower activity moving across the local waters, while a brief thunderstorm developed several miles north of Isabela over the Atlantic waters. This activity was captured by the GOES Geostationary Lightning Mapper (GLM). Overnight temperatures remained within seasonal normals, with minimum temperatures ranging from the lower 70s across the higher elevations to the upper 70s and lower 80s across coastal and urban areas.

A relatively typical weather pattern is forecast today across Puerto Rico and the U.S. Virgin Islands. At the surface, a broad high pressure system across the central Atlantic will maintain steady southeasterly winds across the region. For today, precipitable water values will fluctuate between 1.50 and 1.60 inches as shown by the derived satellite imagery. Although surface moisture remains slightly wet, RH values at 700-500 mb show moisture between the 25th and 50th percentile. Some marginal instability will be present due to divergence aloft; however, temperatures at 500 mb will range between -5 and -6 degrees Celsius and will provide support to generate isolated thunderstorms with the heaviest afternoon convection. Therefore, the forecast calls for shower activity focused across western and northwestern Puerto Rico each afternoon with isolated thunderstorms. Periods of moderate to locally heavy rainfall may result in ponding of water on roads and in poor drainage areas across the northwestern quadrant were a limited flood threat is forecast for today. Meanwhile, warm conditions will continue across the islands, with heat indices ranging from 100 to 108 degrees across urban and coastal areas. Localized higher values cannot be ruled out, particularly across northern and western Puerto Rico. Late Saturday, another pulse of Saharan dust is forecast to move across the northeastern Caribbean, promoting hazy skies and warmer overnight temperatures, with minimum temperatures ranging one to two degrees above climatological normals.

An interesting weather pattern is forecast on Sunday as the combination of Saharan dust particles and increasing low-level moisture associated with an approaching tropical wave affects the local islands. Model guidance suggests precipitable water values increasing between 1.55 and 1.80 inches, supporting greater cloud coverage and shower development across the forecast area. Despite the increase in moisture, the Saharan dust intrusion will continue to promote hazy skies and warm conditions. This pattern will support a more humid weather pattern while maintaining an elevated heat threat across Puerto Rico and the U.S. Virgin Islands. According to the forecast, Sunday is expected to be the warmest day of the short-term period, as suggested by 925 mb temperatures remaining above climatological normals. Heat indices are likely to reach elevated heat threat thresholds across urban, coastal, and even some interior sections of Puerto Rico. By Monday, a drier air mass accompanied by a higher concentration of Saharan dust particles is forecast to filter into the region. This will promote hazy skies, warmer-than-normal temperatures, and a reduction in shower activity, resulting in a generally drier weather pattern across the local islands.

Long Term(Tuesday through Saturday)

Issued at 357 AM AST Sat Jun 6 2026

No major changes were introduced to the long-term forecast. A surface high pressure over the Central Atlantic will maintain easterly winds through Thursday, veering from the southeast by Friday. Pressure gradient will remain weak due to the interaction between the high and a low pressure in the northern Atlantic, slightly weakening winds. Nevertheless, the high should strengthen by the end of the period, increasing the pressure gradient once again and resulting in breezy conditions across the islands. A drier and stable weather pattern will likely dominate on Tuesday and Wednesday as light to moderate concentrations of Saharan Dust will persist on Tuesday afternoon and a drier air mass filtering into the region on Wednesday, limiting shower activity. From the latest model guidance, PWAT values may drop to below climatological normal (between 1.25 and 1.5 inches), with moisture content in the low and mid levels plummeting as well (between 20 and 40 %). Additionally, warmer-than-normal mid-level temperatures (500 mb temperatures above -6 degrees Celsius) which makes it unfavorable for deep convection. Although diurnal heating, local effects, and sea breeze convergence should allow afternoon convection on both days, it will likely remain shallow, presenting a low potential for urban and small stream flooding. By Thursday, guidance suggests an increase in tropical moisture associated with a tropical wave likely to move across the Caribbean Basin, south of the CWA. From the latest deterministic solutions, both GFS and ECMWF show an increase in PWAT values (between 1.6 and 1.8 inches), typical for this time of the year. From a probabilistic perspective, ensemble members tend to wetter solutions, with a low chance of reaching 2.0 inches. Additionally, an upper-level trough deepening into the tropics will gradually cool mid-level temperatures (around -7 degrees Celsius), introducing instability aloft and enhancing deep convection. For this particular scenario, showers will likely move across the U.S. Virgin Islands and portions of eastern Puerto Rico during Thursday morning, while afternoon convection will likely concentrate over interior and western/northwestern Puerto Rico. Showers and isolated thunderstorms will likely lead to ponding of water over roadways and poorly drained areas, along localize minor flooding. As the tropical wave continues to move across the Caribbean Basin, another drier- than-normal airmass will filter into the region, reducing the chance of precipitation on Friday.

The latest model guidance suggests typical warmer-than-normal 925 mb temperatures during the long-term forecast. This, combined with the available moisture, will result in heat indices exceeding 100 degrees Fahrenheit, increasing heat risk across urban areas and low elevations across the islands. Hence, residents and visitors must exercise caution, as these heat levels can affect individuals sensitive to heat, particularly those without effective cooling and/or adequate hydration. A Heat Advisory, particularly on Thursday, may be required.

AVIATION

(06Z TAFS) Issued at 357 AM AST Sat Jun 6 2026

VFR conditions will prevail across all local terminals through the forecast period. SE winds at 10 kt or less will increase after 06/15Z to 15 kt with higher gusts and sea breeze variations. Brief VCSH may affect TJSJ & TJBQ during the morning hours as low-level cloudiness remains in place. By 06/18Z-22Z, localized SHRA may develop across western Puerto Rico, affecting mainly the vicinity of TJBQ with VCTS and possible -TSRA from 06/19Z to 06/21Z. As of 07/06Z, HZ is forecast staring across TISX and TIST.

MARINE

Issued at 357 AM AST Sat Jun 6 2026

An Atlantic surface high-pressure will continue to maintain a tight pressure gradient across the northeastern Caribbean through the period, supporting moderate to fresh easterly winds and choppy seas across the regional waters, particularly the offshore Atlantic waters and Caribbean Passages. A weak tropical wave approaching from the east is expected to cross the local islands on Sunday, resulting in an increase in shower activity and the potential for isolated thunderstorms across the regional waters. Hazy skies associated with a Saharan Air Layer will persist across the region through much of the period, although marine visibilities should generally remain at 6 nautical miles or greater outside of passing showers.

BEACH FORECAST

Issued at 357 AM AST Sat Jun 6 2026

Breezy to locally windy conditions will continue through the weekend and into next week across the region, maintaining a moderate risk of life-threatening rip currents along most local beaches, particularly along north- and east-facing coastlines. Beachgoers are urged to swim only at beaches with lifeguards on duty, remain aware of surf conditions, and avoid venturing too far from shore, as dangerous rip currents remain possible across much of the region.

In addition, afternoon thunderstorms developing primarily across northwestern Puerto Rico may produce frequent lightning, creating hazardous conditions for those at the beach and in the water.

FIRE WEATHER

Issued at 357 AM AST Sat Jun 6 2026

RH % values for today are forecast to remain slighty above the threshold limiting the weather conditions to favor widespread fire danger threat along southern coastal plains. Winds will remain from the southeast up to 15 mph with gusty winds along coastal zones. Based on the forecast weather conditions, we expect a low fire danger risk. Please stay tune for further updates.

SJU WATCHES/WARNINGS/ADVISORIES

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