textproduct: San Juan

KEY MESSAGES

Issued at 256 PM AST Sat Jul 11 2026

* A Red Flag Warning remains in effect through this afternoon for portions of southern and western Puerto Rico due to low relative humidity and breezy conditions. Avoid outdoor burning.

* Above-normal temperatures will persist, with the greatest heat impacts expected from Sunday into early next week.

* Tomorrow into Monday, moisture associated with a tropical wave will increase the potential for showers and isolated t-storms.

* Moderate to high concentrations of Saharan dust will persist through at least early next week, resulting in hazy skies and reduced air quality.

* Moderate to fresh easterly winds, will persist through the weekend, especially across the coastal waters and exposed areas. A moderate risk of rip currents is expected to prevail through early next week.

Short Term(This evening through Monday)

Issued at 256 PM AST Sat Jul 11 2026

Fair weather conditions have prevailed across the local islands through the morning hours under the influence of a dry and stable air mass. GOES satellite imagery continues to show mostly sunny skies with only isolated patches of shallow trade wind cumulus moving across the regional waters, while Doppler radar remains largely free of precipitation. Surface observations indicate notably dry conditions for mid-July, with relative humidity values dropping as low as 41 percent at Camp Santiago during the late morning. Breezy easterly winds have persisted across the islands, with frequent gusts between 25 and 30 mph, with locally higher amounts reported at several coastal and exposed locations. Combined with abundant sunshine, temperatures have warmed efficiently, with highs already reaching the lower 90s across portions of the northern and southern coastal plains. In addition, suspended Saharan dust continues to promote hazy skies and locally reduced visibilities across the islands, a pattern expected to persist through the short- term period, with another pulse of higher dust concentrations forecast to arrive on Monday.

Latest satellite-derived precipitable water estimates continue to indicate a relatively dry air mass over the forecast area, with values near 1.30 inches, while a broad surface high pressure over the central Atlantic and a persistent mid-level ridge extending westward across the northeastern Caribbean maintain moderate to locally fresh easterly winds. The combination of subsidence aloft and limited moisture will continue to suppress widespread convective development for the rest of the afternoon.

The primary weather concern for the rest of the afternoon remains the heat. Strong insolation, limited cloud cover, and 925 mb temperatures remaining near climatological normals will support afternoon highs in the lower 90s across the coastal and urban areas. Although the relatively dry boundary layer has allowed humidity values to fall below typical mid-July levels, peak heat indices may still briefly range between 100 and 105 degrees across the warmest urban and coastal locations. Meanwhile, breezy easterly winds will continue producing occasional gusts between 25 and 35 mph, particularly across coastal areas and higher elevations.

A weak tropical wave approaching the eastern Caribbean on Sunday and moving through the region into Monday is not expected to produce a significant increase in cloud cover or widespread rainfall. The deepest tropical moisture associated with this feature is forecast to remain south of the local islands, with the more active convective activity confined well below the forecast area. Nevertheless, the wave will gradually increase low- and mid-level moisture across Puerto Rico and the U.S. Virgin Islands. Forecast guidance continues to indicate that moisture increases will be most pronounced between 850 and 500 mb, where relative humidity values climb above the climatological 75th percentile, while precipitable water values remain generally within the climatological normal range.

The gradual moistening of the atmospheric column will primarily translate into higher dewpoint temperatures and increasing heat stress, rather than a substantial increase in rainfall coverage. Consequently, widespread afternoon heat indices exceeding 108 degrees become more likely on Sunday and Monday, and Heat Advisories may be required if current trends persist.

Although the approaching wave is relatively weak, daytime heating, local sea-breeze convergence, modest instability aloft, and the increase in low-level moisture should still be sufficient to support scattered afternoon convection across the interior and western sections of Puerto Rico each day. However, the continued presence of Saharan dust and lingering dry air aloft will likely limit the overall coverage and vertical development of thunderstorms. Therefore, while a few locally heavy showers cannot be ruled out across the western interior, the overall rainfall pattern should remain characteristic of a typical summertime regime, with localized impacts confined mainly to areas where showers briefly develop.

Long Term(Tuesday through Saturday)

Issued at 350 AM AST Sat Jul 11 2026

The overall weather pattern during the first half of the long-term period will remain influenced by a weak upper-level trough/nearby upper-level low. This feature will help maintain instability despite a gradual drying trend. Model guidance continues to indicate mid- level relative humidity values ranging between the the and 75th percentiles through Wednesday, while 500-mb temperatures remain relatively cool, around -8 to -9 degrees Celsius. These conditions will support the potential for locally enhanced convection, especially where sea breeze convergence and daytime heating are maximized. The best chance for showers and thunderstorms will be from Tuesday into Wednesday, with passing showers favoring the U.S. Virgin Islands and eastern Puerto Rico during the morning hours, followed by scattered afternoon convection across the interior and western sections of Puerto Rico. Although locally heavy rainfall and isolated ponding of water remain possible, widespread flooding is not anticipated. At the same time, Saharan Air Layer (SAL) intrusion is forecast to affect the region from Tuesday through Thursday. The latest model guidance continues to indicate moderate to locally high concentrations of Saharan dust at times, resulting in hazy skies, reduced visibility, and deteriorating air quality, particularly for sensitive groups. While the upper-level pattern remains somewhat favorable for instability, the presence of the SAL may suppress convective coverage and intensity by introducing drier air aloft and limiting deep cloud development.

From Thursday through Saturday, precipitable water values are forecast to decrease to near or below normals as mid-level temperatures gradually warm and relative humidity decreases. This evolution should promote a more stable environment, limiting shower activity primarily to brief trade-wind showers during the overnight and morning hours, followed by isolated afternoon convection over portions of the western interior of Puerto Rico. Any rainfall should generally remain localized, with a low flooding threat through the latter half of the workweek.

Seasonal to slightly above-normal temperatures are expected throughout the period. Combined with sufficient low-level moisture, afternoon heat indices will likely exceed 100 degrees Fahrenheit across urban and coastal areas, particularly along the northern and southern coastal plains of Puerto Rico and portions of the U.S. Virgin Islands. In addition, the presence of Saharan dust may reduce overnight radiational cooling, leading to warmer-than-normal minimum temperatures and maintaining an elevated heat risk through much of the workweek despite the gradual drying trend.

AVIATION

(18Z TAFS) Issued at 256 PM AST Sat Jul 11 2026

Mainly VFR conds will prevail across all TAF sites thru the fcst pd. HZ due to lingering Saharan dust will continue acrs the local islands, with sfc vsbys generally remaining 6SM. E-ESE sfc winds at 15-25 kt with freq gusts up to 30 kt will persist thru around 11/22Z, becoming lgt/vrb overnight. Brief VCSH may affect the vcnty of TJBQ late this aftn, but no sig operational impacts are expected.

MARINE

Issued at 256 PM AST Sat Jul 11 2026

A broad surface high pressure positioned over the central Atlantic will maintain a tight pressure gradient across the northeastern Caribbean. Moderate to fresh easterly winds are present across the regional waters, with occasional strong winds, particularly over the offshore Caribbean waters through at least tomorrow, Saturday. These conditions will continue to support choppy to hazardous seas, especially across the offshore Caribbean waters and the Mona Passage. Small Craft Advisories remain in effect for the affected waters through at least midnight tonight. Moderate to high concentrations of Saharan dust will also persist through the weekend and into early next week, resulting in hazy skies and reduced visibility.

BEACH FORECAST

Issued at 256 PM AST Sat Jul 11 2026

Wind-driven seas and moderate to fresh easterly winds will maintain a moderate risk of rip currents across most beaches of Puerto Rico and the U.S. Virgin Islands through early next week. As a result, life-threatening rip currents will remain possible in the surf zone each day, and beachgoers are urged to exercise caution. By midweek, the risk is forecast to decrease to low. However, life-threatening rip currents can still occur in the vicinity of groins, jetties, reefs, and piers.

Additional beach hazards include the presence of Saharan dust, which will continue to promote hazy skies, reduced air quality, and warm to hot conditions during the peak afternoon hours. Sensitive groups should consider limiting prolonged outdoor exposure due to the reduced air quality associated with Saharan dust, while everyone is encouraged to stay hydrated and use caution if spending time at the beach.

FIRE WEATHER

Issued at 256 PM AST Sat Jul 11 2026

Current observations at Cabo Rojo and Camp Santiago continue to indicate critical fire weather conditions across portions of southern Puerto Rico. Surface observations have shown relative humidity values between 40 and 50 percent, particularly across the southern coastal plains, while sustained easterly winds of 15 to 20 mph with frequent gusts between 25 and 35 mph persist.

Combined with ongoing dry conditions and critically dry fuels resulting from persistent rainfall deficits, conditions remain favorable for rapid fire growth and spread across much of Puerto Rico, Vieques, Culebra, and St. Croix. Therefore, the Red Flag Warning remains in effect through 5 PM AST for the southern coastal plains and hills of Puerto Rico, while the Fire Danger Statement continues for the remaining areas.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Red Flag Warning until 5 PM AST this afternoon for PRZ014-015- 018-027.

VI...None. AM...Small Craft Advisory until midnight AST tonight for AMZ711-733- 741.