textproduct: San Juan

KEY MESSAGES

Issued at 350 AM AST Sat Jul 11 2026

* Above-normal temperatures will persist today with maximum temperature in +2 or +3 degrees from normals, enhancing warm conditions across urban sections and some western coastal areas.

* Moderate to fresh easterly winds, occasionally strong, will persist through early next week, especially across coastal waters and exposed areas.

* For most of the short term period, moderate to high concentrations of Saharan dust will result in hazy skies and reduced air quality and limited shower activity.

* From Sunday into Monday, a tropical wave is expected to increase moisture across the region, increasing to a higher potential for showers and isolated thunderstorms.

* For today, elevated to critical fire weather conditions will continue through the weekend due to dry soils, low relative humidity, and breezy conditions.

Short Term(Today through Monday)

Issued at 350 AM AST Sat Jul 11 2026

Fair and tranquil weather conditions prevailed across the County Warning Area (CWA) throughout the overnight hours. Satellite imagery indicated minimal cloud coverage, with expansive areas of mostly clear skies dominating the region. Additionally, local radar observed a dry and stable environment, with no significant shower activity detected across the islands or the surrounding coastal waters. Overnight low temperatures remained warm, hovering in the upper 70s across the western plains and most coastal areas, while the San Juan metropolitan area experienced lows in the lower 80s. Meanwhile, much cooler conditions were observed across the higher elevations of the central interior, where minimum temperatures comfortably dropped into the low to mid-70s.

Precipitable water (PWAT) derived from satellite imagery shows a drier air mass dominating the local region today, with PWAT values around 1.30 inches. At the surface, a broad high-pressure system over the central Atlantic extending into the Caribbean, coupled with strong high pressure at the 700 mb level located over the western Atlantic, will maintain a steady easterly wind flow. Within the lowest 3 kilometers (1000-700 mb layer), sustained winds will range from 12 to 16 mph, with gusty conditions occasionally reaching up to 30 mph. Given the suppressed moisture profile and widespread subsidence, conditions call for a mostly dry day with limited cloudiness. There is only a very low chance of localized, short-lived afternoon showers along the western interior sections, and no flooding impacts are expected across the islands.

Regarding the HEAT THREAT today, impacts will be heavily driven by daily temperatures rather than deep available moisture. Due to the aforementioned lack of cloud cover allowing for maximum solar insolation, daytime high temperatures are forecast to rapidly climb 2 to 3 degrees above climatological normals, reaching the lower 90s across the southwestern and south-central plains, as well as the San Juan metropolitan area. Furthermore, model guidance at the 925 mb level indicates temperatures staying around the 50th percentile, which supports this significant diurnal warming trend. The breezy easterly winds in the lower levels will allow drier air to mix down to the surface, which typically limits widespread excessive humidity. However, particularly between 12 PM and 2 PM, localized heat indices are expected to briefly peak between 106 and 108 F, specifically across the San Juan metro area and the western coastal municipalities between Anasco and Aguada. Because these peak heat values of 106 to 108 F will be highly localized, a Heat Advisory will not be issued for today. However, residents are urged to stay hydrated, avoid strenuous outdoor activities, and take breaks in the shade when working outdoors.

Conditions for Sunday and Monday will change as the moisture field from a distant tropical wave moving well south of the islands increases the frequency of cloudiness and occasional passing showers across the area. Accompanying this moisture, which is forecast to remain on the lower side of climatological normals, another pulse of Saharan dust will move in. These moderate dust concentrations will result in hazy skies across the region. Therefore, the forecast for these days includes morning passing showers across eastern sections, followed by localized afternoon convection across the western interior sections. In terms of the heat threat, conditions will become more favorable for widespread heat indices between 104 and 108 F. The influx of low-level moisture will increase dewpoint temperatures, and when combined with good periods of daytime solar radiation, there is a medium to high probability that Heat Advisories will be required if these conditions materialize. Residents and visitors are urged to stay tuned for further weather updates and to remain hydrated throughout the day.

AVIATION

(06Z TAFS) Issued at 350 AM AST Sat Jul 11 2026

VFR conditions are expected to prevail across all terminals during the next 24 hours. A very dry air mass will maintain mostly clear skies, limiting cloudiness to only a FEW high-level clouds. Hazy skies due to suspended Saharan dust particles could slightly reduce surface visibility at times.. Mainly easterly surface winds at around 10 to 13 kts will persist through the early morning, increasing to around 15 to 18 kts with higher gusts by 11/15Z.

MARINE

Issued at 350 AM AST Sat Jul 11 2026

A broad surface high pressure centered over the central Atlantic, combined with a low pressure over northern South America, will maintain a tight pressure gradient across the northeastern Caribbean through at least this evening. This pattern will support moderate to fresh easterly winds with occasional strong gusts, particularly across the offshore Caribbean waters. These conditions will maintain choppy to hazardous seas, especially across the offshore Caribbean waters and the Mona Passage. Moderate to high concentrations of Saharan dust will persist through the weekend, producing hazy skies and reduced visibility. A weak tropical wave is expected to move across the local waters around Sunday, increasing the risk of showers and thunderstorms, along with locally higher winds and seas near the strongest activity.

FIRE WEATHER

Issued at 350 AM AST Sat Jul 11 2026

Conditions are highly favorable for rapid fire dispersion across the region today. Surface observations have been indicating relative humidity values dropping into the lower 50s, generally ranging between 50 and 60 percent, particularly across the southern coastal plains of Puerto Rico. This significantly dry air mass is being accompanied by breezy conditions, with sustained easterly winds between 15 and 18 mph and frequent wind gusts between 25 and 30 mph. Given these breezy and dry conditions, coupled with persistent rainfall deficits, critically dry fuels continue across much of Puerto Rico, Vieques, Culebra, and St. Croix. Therefore, a Fire Danger Statement remains in effect today. Additional fire weather products may be needed through the weekend, particularly tomorrow, Saturday; please stay tuned to the forecast.

SJU WATCHES/WARNINGS/ADVISORIES

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