textproduct: San Juan

KEY MESSAGES

Issued at 123 PM AST Tue Jun 30 2026

* Moderate to high concentrations of Saharan dust will persist this afternoon, resulting in hazy skies, reduced visibility, and poor air quality. Low to moderate concentrations are expected through the next several days before increasing again by the holiday weekend.

* Limited shower activity is expected across the islands each day. However, localized afternoon showers and a few isolated thunderstorms remain possible across northwestern Puerto Rico.

* Warm to hot conditions will continue, with heat indices reaching or exceeding 105 degrees F across urban and low-lying areas.

* Moderate to locally fresh easterly winds will maintain locally choppy seas across the regional waters. Small craft operators should exercise caution, especially in exposed waters.

Short Term(This evening through Thursday)

Issued at 123 PM AST Tue Jun 30 2026

A strong Saharan Air Layer (SAL) is spreading across the northeastern Caribbean today, bringing widespread hazy skies and significantly limiting rainfall potential over the islands. For the remainder of this afternoon, this hostile environment will keep most of the islands dry, with reduced visibility and degraded air quality. The only exception will be over the interior and western portions of Puerto Rico, where localized sea breeze convergence and intense diurnal heating may briefly overcome the capping inversion to produce isolated afternoon showers and a brief thunderstorm.

Over the next few days, the core of the SAL will gradually move west of the region, leading to a gradual decrease in dust concentrations. However, minor to moderate concentrations of suspended particulates will remain in place, keeping skies slightly hazy through the end of the short-term period. As the dust layer exits, a gradual recovery in low-level moisture and a weakening of the trade wind cap inversion will allow a more typical seasonal weather pattern to return. This transition will support a slow increase in overnight and early morning trade wind showers brushing the windward coasts, followed by development of scattered afternoon showers and isolated thunderstorms over the western and interior sections of Puerto Rico driven by local effects and heating.

Primary impacts through Thursday will focus on the lingering hazy conditions and heat risk. While air quality and visibility will be at their lowest today, individuals with respiratory sensitivities should remain cautious through Thursday as moderate dust concentrations persist. Likewise, the combination of strong solar radiation under mostly sunny skies and recovering low-level moisture will cause daytime temperatures in the upper 80s and lower 90s to feel significantly hotter. Heat indices are forecast to easily reach the triple digits across lower elevations, coastal areas, and urban areas.

Long Term(Friday through Tuesday)

Issued at 321 AM AST Tue Jun 30 2026

The long-term forecast remains on track. A transition from a relatively dry and hazy air mass to a highly saturated and unstable tropical environment is anticipated across the local area. At the surface, a dominant high pressure system over the Central Atlantic will maintain the local pattern under southeasterly winds, fluctuating at times, particularly during the morning hours. Aloft, a 250 mb cut-off low will remain anchored near the region throughout the entire forecast period, providing continuous upper-level support and maintaining a marginally unstable environment with 500 mb temperatures forecast to range between -8 C and -7 C. From Friday into Saturday, despite the instability aloft, available moisture will remain relatively shallow and trapped below the 850 mb level. The NASA Goddard aerosol model guidance again indicates a mass of Saharan dust moving across the region, which will promote hazy skies and effectively suppress widespread convective activity. Consequently, residents can expect a variable weather pattern characterized by hot conditions and limited rainfall accumulations, though brief morning showers across eastern Puerto Rico and isolated afternoon convection over the western interior and northwestern sectors cannot be entirely ruled out due to local effects and daytime heating.

From Sunday into Tuesday, the latest global model guidance from both the ECMWF and GFS indicates an increase in mid-level moisture, with increasing relative humidity values at the 700 mb level arriving in the region. This will enhance a variable weather pattern, boosting the development of afternoon convection across the western and northwestern interior of Puerto Rico. Meanwhile, Saharan dust concentrations will gradually diminish, allowing low-level moisture to become more uniform by Monday. By Tuesday, a significant increase in deeper atmospheric moisture is highly anticipated across the northeastern Caribbean as a tropical wave approaches and moves through the local area. The arrival of tropical moisture, combined with the favorable upper-level dynamics provided by the persistent cut-off low, will erode any remaining stable layers and allow precipitable water values to expand well above normal levels. This interaction will result in an increase in widespread shower and isolated thunderstorm activity across the region, bringing a limited to elevated potential for localized ponding of water on roadways and in poorly drained areas. Regardless of the changing moisture levels, persistently warm conditions will dominate coastal and urban sectors for the entirety of the long-term period. An elevated heat threat will remain present each day, with maximum heat index values consistently peaking between 100 and 108 F across portions of the north-central coastal plain and southern Puerto Rico during the peak heating hours.

AVIATION

(18Z TAFS) Issued at 123 PM AST Tue Jun 30 2026

Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. However, iso SHRA and -TSRA could develop in and around TJBQ btw 30/18-22z, causing tempo MVFR conds. HZ due to Saharan dust will continue to reduce VSBY to near 6SM. The 30/12z TJSJ sounding indicated ESE winds up to 23 blo FL080.

MARINE

Issued at 123 PM AST Tue Jun 30 2026

Surface high pressure across the central Atlantic, in combination with a frontal low over the western Atlantic, will promote moderate to locally fresh easterly winds. This will maintain locally choppy marine conditions, especially across the Atlantic waters and local passages over the next several days. Therefore, small craft should continue to exercise caution.

Reduced visibility due to moderate to high concentrations of Saharan dust will persist through at least tonight, with low to moderate concentrations expected over the following days. An additional surge of Saharan dust is forecast to begin filtering into the region next weekend. Mariners should remain alert for locally hazardous conditions in and near passing showers.

BEACH FORECAST

Issued at 123 PM AST Tue Jun 30 2026

Tonight, and through the rest of the workweek, the risk of rip currents is forecast to remain low. However, life-threatening rip currents can still occur in the vicinity of jetties, reefs, and piers. As a result, beachgoers are always encouraged to remain cautious. By the end of the week and into the weekend, the risk of life-threatening rip currents is expected to increase to a moderate level, meaning rip currents will be possible in the surf zone, as winds become breezier.

Additional beach hazards include the presence of Saharan dust, which will result in hazy skies and reduced air quality, warm to hot conditions during peak heating hours, and isolated thunderstorms, particularly across the northwestern beaches of Puerto Rico each afternoon.

SJU WATCHES/WARNINGS/ADVISORIES

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