textproduct: San Juan

KEY MESSAGES

Issued at 324 AM AST Sun Jun 28 2026

* Dry conditions along with low concentrations of Saharan dust will prevail today across Puerto Rico and the U.S. Virgin Islands.

* An approaching tropical wave will bring deep tropical moisture into the area from late tonight into Tuesday morning, enhancing the potential for showers and isolated thunderstorms.

* Warmer to hot conditions are expected for the next few days, with heat indices exceeding 100F across urban and coastal areas of Puerto Rico and the U.S. Virgin Islands. Stay hydrated.

* There is a low risk of rip current across all islands through early this week.

Short Term(Today through Tuesday)

Issued at 324 AM AST Sun Jun 28 2026

Isolated to scattered showers were seen overnight, affecting portions of northern and eastern Puerto Rico as well as the regional waters; however, rainfall accumulations were minimal. Across the U.S. Virgin Islands, calm and fair weather conditions prevailed for most of the night. Minimum temperatures ranged from the low to mid- 70s across coastal and urban areas of Puerto Rico, and from the low to mid-60s in higher elevations, while staying in the low 80s across Vieques, Culebra, and the U.S. Virgin Islands. Winds prevailed from the east-southeast at 5 to 10 mph with local land breeze variations.

Today, a drier air mass will gradually filter into the area along with low concentrations of Saharan dust. Precipitable water (PWAT) values will drop below normal, ranging between 1.20 and 1.40 inches through the afternoon hours. Therefore, generally fair weather conditions will prevail today. A few passing showers are possible this morning across the U.S. Virgin Islands and eastern Puerto Rico, followed by locally induced showers across northwestern Puerto Rico this afternoon due to the combination of daytime heating and local effects. In addition, hazy skies and slightly reduced visibilities are anticipated as the Saharan dust moves in. Under this weather scenario, temperatures will rise into the upper 80s to low 90s across coastal and urban areas, and into the low to mid-80s in the mountains. Heat indices across the region will reach or surpass 100F, particularly during the peak heating hours of the day. Residents and visitors are urged to practice heat safety by staying hydrated, limiting strenuous outdoor activities, and taking frequent breaks in shaded or air-conditioned areas.

By Sunday night into early Monday, deep tropical moisture associated with an approaching tropical wave, currently located east of the Lesser Antilles, will begin to filter into the region. This wave will rapidly increase PWAT values across the area to above-normal levels of up to 2.20 inches. As the wave approaches, atmospheric instability will also increase, with 500 mb temperatures dropping to -8C to -9C, enhancing the potential for thunderstorm activity. Showers and isolated thunderstorms are expected across the region from Monday into Tuesday morning, elevating the risk of flooding across northern and eastern portions of Puerto Rico. Potential impacts include ponding of water on roadways, urban and small-stream flooding, and localized flash flooding. Gusty winds will also be possible within the heavier shower activity. Regardless of these risks, the incoming rainfall will be highly beneficial for areas currently experiencing abnormally dry, moderate, or severe drought conditions across the islands.

Long Term(Wednesday through Sunday)

Issued at 324 AM AST Sun Jun 28 2026

A broad surface high pressure system centered over the central Atlantic and extending into the Caribbean will remain the dominant weather feature through the long-term period, maintaining a predominantly southeasterly low-level wind flow across Puerto Rico and the U.S. Virgin Islands. Embedded patches of moisture with precipitable water values fluctuating near climatological normals will continue to move across the local area from Wednesday into Thursday, promoting a variable weather pattern. While widespread rainfall is not anticipated, daytime heating, local effects, and available moisture will support the development of afternoon showers and isolated thunderstorms across portions of western Puerto Rico each day. Some of the strongest showers could produce localized ponding of water on roadways and in poorly drained areas. Aloft, a cutoff low at 250 mb will gradually approach the northeastern Caribbean, lowering temperatures near the 250 mb level to around -9 C. This feature will provide modest upper-level support and slightly enhance atmospheric instability, favoring locally stronger convection during the afternoon hours. In addition, a small area of Saharan dust is expected to move across the region on Wednesday, resulting in hazy skies and reduced visibility at times before concentrations gradually diminish on Thursday.

From Friday through Sunday, a much drier air mass will filter into the region from the surface to around 700 mb, reducing moisture availability and overall shower coverage. Precipitable water values are expected to range between 1.5 and 1.7 inches, while relative humidity between 850 and 500 mb will remain near to slightly below climatological normals. Another pulse of Saharan dust is also forecast to move across the northeastern Caribbean during the weekend, leading to hazy skies and further suppressing shower activity. Despite the drier conditions, isolated afternoon showers cannot be completely ruled out over the western interior of Puerto Rico due to local sea breeze convergence and daytime heating. Warm to hot conditions will persist throughout the forecast period, with a daily elevated heat threat expected across the islands. Heat index values will generally range from 100 to 108 degrees, with isolated locations reaching around 110 degrees, particularly across the north- central coastal plain and the western interior of Puerto Rico during the peak heating hours between 10 AM and 5 PM each day.

MARINE

Issued at 324 AM AST Sun Jun 28 2026

Trade wind perturbations moving near the region will promote a moderate east-southeast wind flow across the islands today. Then a tropical wave will cross the Lesser Antilles, with it leading edge reaching the US Virgin Islands from this evening into the early Monday morning, bringing gusty winds and lightning, creating localized hazardous conditions for small craft. The surface high pressure will increase the local pressure gradient promoting the return of moderate to locally fresh east to east-southeasterly winds and choppy seas.

BEACH FORECAST

Issued at 324 AM AST Sun Jun 28 2026

The risk of rip currents is low for this morning for the USVI and PR. Although we have a low risk, beachgoers should be aware of the possibility of life-threatening rip currents near groins, jetties, reefs, and piers.

The risk will turn moderate for the northern and northwest coast of PR from this evening onward, with the addition of St Croix, Vieques and Culebra by Monday and Tuesday as well. The moderate risk means that life-threatening rip currents are possible in the surf zone.

Besides rip currents, showers and isolated thunderstorms may move near coastal areas of the islands around Monday with the approaching tropical wave. Beachgoers are encouraged to monitor weather conditions, as isolated thunderstorms may bring heavy rainfall, gusty winds, and lightning.

SJU WATCHES/WARNINGS/ADVISORIES

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