textproduct: San Juan

KEY MESSAGES

Issued at 340 AM AST Sun Jul 12 2026

* Moisture from a tropical wave passing south of the region will increase today and Monday, leading to a higher potential for showers across portions of western and interior Puerto Rico. The additional moisture will also contribute to heat indices ranging from 100 to 111F.

* A Heat Advisory is in effect today from 10 AM to 5 PM. Heat indices are expected to reach dangerous levels, ranging between 100 and 111F in some areas.

* Moderate concentrations of Saharan dust will persist across the islands today, resulting in hazy skies and reduced visibility at times.

* Breezy conditions will persist today, with moderate to fresh easterly winds expected across the region. These winds may result in choppy marine conditions and create difficult conditions for some outdoor and marine activities.

* A moderate risk of rip currents continues across several local beaches. Life-threatening rip currents are possible, especially near piers, jetties, and sandbars.

Short Term(Today through Tuesday)

Issued at 340 AM AST Sun Jul 12 2026

Fair weather conditions prevailed across the County Warning Area (CWA) throughout the overnight hours. Satellite imagery indicated minimal cloud coverage, with expansive areas of clear skies dominating the region. Additionally, local radar observed a dry and stable environment, with no shower activity detected across the islands or the surrounding coastal waters. Overnight low temperatures remained warm, in the upper 70s to lower 80s across the coastal and metropolitan areas, while temperatures across the higher elevations of the central interior dropped into the low to mid-70s. As the morning progresses, a light haze will begin to overspread the region due to an incoming pulse of Saharan dust.

A broad surface high pressure over the central Atlantic extending into the Caribbean will hold an easterly wind flow with sustained winds between 12-15 mph and some gusty winds. The presence of Saharan dust particles will remain in place across the region during the day, resulting in hazy skies and warm temperatures throughout the day. As the day progresses, the moisture field from a distant tropical wave moving well south over the Caribbean Sea will gradually move low-level moisture into the region. The moisture available will enhance a variable pattern across the area with an increase in the showers' development as well as high chances of observed heat indices that could reach 108 and 110 degrees. Having said that, for today, the heat threat will remain elevated, and a heat Advisory is in effect from 10 AM to 5 PM AST across all coastal areas and the vicinity of Caguas in Puerto Rico and the U.S. Virgin Islands. In terms of showers, Hi-Resolution models and the NBM model suggest rainfall activity along western interior areas. Although showers will remain quite limited in coverage due to the presence of the Saharan Dust particles, the heaviest showers can result in some low-lying water accumulations.

By Monday, the surface high pressure will maintain steady easterly winds below 3 kilometers, pushing a moisture field trailing over the islands. This will increase precipitable water (PWAT) values by 1.7 to 1.8 inches, making Monday the day with the highest probability of shower activity. In fact, the GFS-based Galvez- Davison Index (GDI) shows enhanced afternoon showers across the western interior and western Puerto Rico, with a low probability for one or two isolated thunderstorms embedded within the heaviest downpours. On Tuesday, dry weather will quickly return as the moisture leaves the area and strong stability takes over under the upper-level ridge. A dense layer of Saharan dust will cover the region, causing hazy conditions and suppressing most daytime rain development. Along with the dry air, a limited to elevated heat threat will develop due to maximum solar radiation and easterly winds. This will increase daytime temperatures, pushing heat indices between 100 and 108 F across coastal and urban areas. Furthermore, the combination of these hot temperatures, low relative humidity values, and breezy easterly winds will maintain critically dry fuels and a high fire danger risk, especially along the southern plains of Puerto Rico. For beachgoers and mariners, the breezy conditions will also maintain choppy seas and a moderate risk of rip currents across most local beaches.

Long Term(Wednesday through Sunday)

Issued at 340 AM AST Sun Jul 12 2026

From Wednesday through Saturday, the primary impacts will be periods of hazy skies, reduced visibility, poor air quality, and hot daytime conditions as a Saharan Air Layer (SAL) affects the region. Moderate to locally high concentrations of Saharan dust are expected Wednesday through Thursday, resulting in the greatest impacts during this long term period, particularly for sensitive individuals in areas of thicker dust concentrations. Dust concentrations should gradually decrease toward the weekend, although some haze may linger through Saturday.

Shower activity will generally remain limited throughout the period. On Wednesday, passing trade-wind showers will favor the U.S. Virgin Islands and eastern Puerto Rico during the morning, followed by isolated to scattered afternoon showers across the interior and western sections of Puerto Rico. An increase in low and mid-level moisture on Thursday may result in slightly greater shower coverage. However, warm mid-level temperatures, modest lapse rates, and the lingering influence of the SAL will maintain a relatively stable atmosphere, preventing widespread deep convection. By Friday and Saturday, moisture decreases to near or below normals while stable mid-level conditions persist, limiting rainfall mainly to brief trade-wind showers and isolated afternoon convection over western Puerto Rico. No flooding concerns are anticipated through the period.

Seasonal to slightly above-normal temperatures are expected throughout the period. Combined with abundant sunshine and 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. The presence of Saharan dust through Thursday may also limit overnight radiational cooling, resulting in warmer-than-normal minimum temperatures and prolonging heat stress despite the gradual drying trend.

AVIATION

(06Z TAFS) Issued at 340 AM AST Sun Jul 12 2026

VFR conditions will prevail for the forecast period along the TAF sites. Saharan dust will continue to affect the region, resulting in HZ. E winds will persist between 12 and 18 knots, with higher gusts between 20 and 25 knots possible. Showers will mainly affect the western interior of PR resulting in brief periods of lower ceilings and reduced visibility, especially near TJBQ from 12/19Z to 12/21Z. Winds will gradually diminish during the overnight hours, with VFR conditions expected to continue.

MARINE

Issued at 340 AM AST Sun Jul 12 2026

A weak tropical wave will move well south of the local islands across the Caribbean Sea today. Meanwhile, strong Atlantic high pressure will maintain moderate to locally fresh easterly to east- northeasterly winds, resulting in choppy seas across the regional waters. The high pressure will strengthen through early next week, tightening the local pressure gradient and sustaining moderate to fresh east to east-southeast winds and hazardous marine conditions.

BEACH FORECAST

Issued at 340 AM AST Sun Jul 12 2026

Breezy trade winds will continue to create a moderate risk of life- threatening rip currents along many beaches across Puerto Rico and the U.S. Virgin Islands today. Through the middle of the week, the rip current risk will remain elevated, particularly along north- and east-facing beaches. Beachgoers should swim near lifeguards whenever possible, heed beach warning flags, and never swim alone. An elevated extreme heat risk is also expected along many beaches today and through the first half of the week. Stay well hydrated, seek shade whenever possible, and apply sunscreen to help reduce the risk of heat-related illnesses.

This afternoon, isolated thunderstorms may develop over western Puerto Rico. If you are at the beach or participating in outdoor activities, remain alert for lightning. Remember: When thunder roars, go indoors. Move to a substantial building or a hard-top vehicle immediately.

FIRE WEATHER

Issued at 340 AM AST Sun Jul 12 2026

Despite drier airmass is dominating the local region now, an increase in moisture is expected as the day progresses increasing the RH values staying in the low to mid 50s across the southern coastal areas. Winds will remain from the E-NE, becoming from the E at 10 AM up to 15 mph and slightly higher across coastal areas. The increase in moisture will enhance shower activity for the western interior sections by this afternoon. Therefore, the fire danger threat will remain moderate for today.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for PRZ001>005-007-008-010>013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for VIZ001-002.

AM...None.