textproduct: San Juan

KEY MESSAGES

Updated at 335 AM AST Mon Jun 1 2026

* High concentrations of Saharan dust will promote hazy skies, poor air quality, and reduced visibilities through Tuesday. Another pulse of moderate concentrations is expected by the end of the workweek.

* Hot temperatures are expected in general, particularly along the lower elevations and urban areas of the islands.

* Limited shower activity expected across the region for the next few days.

Short Term(Today through Wednesday)

Issued at 335 AM AST Mon Jun 1 2026

A predominantly dry, stable, and hazy weather pattern will prevail across Puerto Rico and the U.S. Virgin Islands through mid-week, driven by a prominent Saharan Air Layer (SAL) and persistent mid- level ridging. Recent satellite-derived Total Precipitable Water (TPW) imagery and the 01/00Z TJSJ sounding confirm a hostile environment for deep convection, with precipitable water values between 1.25 and 1.40 inches, which are below seasonal normals for early June. The sounding also indicated a trade wind inversion alongside aggressive mid-level drying, which GFS forecast soundings shows 700-500mb relative humidity remaining suppressed through Wednesday. Furthermore, NASA aerosol optical thickness data reveals a dense plume of suspended Saharan dust thoroughly entrenched over the northeastern Caribbean, promoting hazy skies and the potential for degraded air quality over the coming days.

Consequently, high-resolution ensemble rainfall guidance heavily suppress precipitation across the entire forecast through the forecast period. While a few shallow, fast-moving trade wind showers cannot be entirely ruled out across the U.S. Virgin Islands and windward coastal areas of eastern Puerto Rico during the overnight and early morning hours, or highly localized, afternoon diurnally driven showers over western Puerto Rico and from streamers developing downwind of the islands. The daily total rainfall accumulations will remain limited to none across most areas. Residents and visitors should anticipate hot, distinctly hazy, and mostly dry conditions persisting across the islands through at least Wednesday.

Long Term(Thursday through Monday)

Issued at 335 AM AST Mon Jun 1 2026

Overall, a drier weather pattern is expected to prevail throughout much of the long-term period, limiting shower activity across Puerto Rico and the U.S. Virgin Islands. A dominant mid-level ridge will continue to promote dry and stable conditions aloft. At the upper levels, an upper-level low will remain well east of the local islands and the Lesser Antilles, enhancing subsidence across the northeast Caribbean. Meanwhile, at the surface, a strong Azores High will continue to drive breezy southeasterly winds through early next week.

Under this pattern, mainly fair weather conditions are anticipated to persist, supported by below-normal precipitable water (PWAT) values of approximately 1.0 inch for this time of the year, particularly in early June. Even as drier air dominates, embedded patches of low-level moisture will filter into the area from time to time. This will bring brief, fast-moving showers to portions of eastern Puerto Rico and the U.S. Virgin Islands during the morning hours, followed by locally driven showers in the afternoon. The potential for isolated thunderstorms remains low, as mid-level temperatures at 500 mb are forecast to remain well above normal at a warm -4C. Consequently, any afternoon shower activity will be short- lived and confined to portions of central and northwestern Puerto Rico. The latest model guidance indicates that by Friday into Saturday, a weak tropical wave will pass well south of the area. While some peripheral moisture from this wave may reach the islands, impacts are expected to be minimal.

Furthermore, another plume of moderate Saharan Air Layer is forecast to arrive and persist through the upcoming weekend, resulting in hazy skies, reduced visibilities, and poor air quality. Sensitive groups, particularly individuals with respiratory conditions should take necessary precautions to limit outdoor exposure and seek medical recommendations.

AVIATION

(06Z TAFS) Issued at 335 AM AST Mon Jun 1 2026

Mainly VFR conditions expected to prevail during the next 24 hours. HZ and VSBY near 6SM due to Saharan dust. Sfc winds fm the ESE at 12-16 kt with stronger gusts and sea breeze variations aft 01/13z.

MARINE

Issued at 335 AM AST Mon Jun 1 2026

A surface high will tighten the local pressure gradient, resulting in moderate to fresh east-to-east-southeast winds, promoting choppy seas across the regional waters through much of the week. An extensive Saharan Air Layer will linger across the region through much of the workweek. Trade wind showers are expected to increase by midweek.

BEACH FORECAST

Issued at 335 AM AST Mon Jun 1 2026

The increasing winds and choppy seas will promote the possibility of life-threatening rip currents across the region throughout the week. Therefore, there is a moderate risk of rip currents for the majority of exposed beaches in PR and the USVI. Always swim near a lifeguard and remember to heed the advice of the local beach patrol and flag warning systems.

Moderate to high concentrations of Saharan dust will persist through much of the week, resulting in hazy skies and reduced air quality. Moisture associated with a trade wind perturbation will increase the potential of rain around Wednesday, with passing showers across windward areas and afternoon convection over western Puerto Rico.

SJU WATCHES/WARNINGS/ADVISORIES

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