textproduct: San Juan

KEY MESSAGES

Issued at 100 PM AST Sat Oct 3 2026

- Showers and thunderstorms will continue to bring localized heavy rainfall, flooding, frequent lightning, and gusty winds over the next few days, especially during the afternoon. The potential for more widespread and heavier activity will increase Wednesday into Thursday as moisture associated with a tropical wave moves into the region.

- Heat concerns will increase Sunday into Monday and remain elevated through much of next week.

- Marine conditions will become more favorable for small craft Sunday onward. A moderate risk of rip currents will continue along many north- and east-facing beaches through Sunday, briefly decrease Monday, and return Tuesday.

- Across the U.S. Virgin Islands, heat will remain the main concern, while shower activity may increase Wednesday into Thursday as deeper tropical moisture reaches the region.

Short Term(This evening through Monday)

Issued at 100 PM AST Sat Oct 3 2026

Showers and thunderstorms left over from the afternoon should gradually diminish with the loss of daytime heating, with some activity lingering across the interior and western Puerto Rico before fading this evening. Later tonight, a more typical overnight pattern should return, with passing showers favoring eastern Puerto Rico and the U.S. Virgin Islands. Winds will become light and variable in many areas overnight, with lows in the upper 70s across coastal areas and near 80 degrees in some of the more exposed locations. Temperatures across the higher elevations and interior valleys should fall into the lower 60s.

Sunday and Monday will feature a fairly typical diurnal pattern. Low-level winds will gradually become more east-southeasterly while the mid- to upper-level trough remains displaced near Hispaniola, leaving Puerto Rico along its eastern periphery with only modest large-scale forcing. Model guidance shows seasonal to slightly above-seasonal moisture through the period, but relatively modest mid-level moisture and weakening lapse rates should limit the potential for more widespread or organized convection. Therefore, daytime heating, sea-breeze convergence, terrain effects, and localized moisture will remain the primary drivers for afternoon shower and thunderstorm development, mainly along the Cordillera Central and toward western and northwestern Puerto Rico. General winds will remain around 10 to 15 mph, with locally gusty winds near thunderstorms.

Heat concerns will increase Sunday into Monday as low-level temperatures continue to rise. The focus each day will then shift from heat during the late morning and early afternoon to localized heavy rainfall and flooding concerns where thunderstorms develop. Although flooding is expected to remain localized, the risk will be greater in areas that have received repeated rainfall in recent days, where soils remain moist and opportunities for drying have been limited.

Long Term(Tuesday through next Friday)

Issued at 100 PM AST Sat Oct 3 2026

For the long-term period, more seasonal conditions are expected initially, with a broad high-pressure system over the central Atlantic remaining the main surface feature. On Tuesday, an east- southeasterly low-level flow will favor a relatively fair morning with limited shower activity, followed by afternoon convection supported mainly by lingering low-level moisture, daytime heating, and local effects. Activity should focus toward the interior and northwestern portions of Puerto Rico, while streamers from the U.S. Virgin Islands, Vieques, and Culebra remain possible.

On Wednesday, moisture associated with a tropical wave passing south of the islands should begin filtering into the CWA within the east-southeasterly flow, increasing the frequency and intensity of showers and thunderstorms across the local waters and over the interior and northwestern portions of Puerto Rico. Moisture should deepen considerably Wednesday into Thursday, with PWAT values potentially reaching around 2.1 to 2.4 inches and increasing moisture through the lower and mid-levels. By Thursday, nearby mid- to upper-level troughing, including an upper-level low near Hispaniola, may provide additional support aloft. Despite rather modest lapse rates and relatively warm mid-level temperatures, the combination of deeper moisture, daytime heating, and periods of enhanced upper-level support should favor the most active portion of the period Wednesday into Thursday. Locally heavy rainfall and repeated downpours could increase the potential for urban and small-stream flooding, with localized flash flooding possible where the heaviest activity persists.

By Friday, a transition toward a drier pattern is expected as deeper moisture moves away and mid-level moisture decreases sharply. Lingering low-level moisture, daytime heating, and local effects should still support afternoon convection, while a more easterly low-level flow favors activity across the interior and western half of Puerto Rico. A drier air mass should spread across the islands Saturday, further limiting deep convection. Heat will remain another concern through much of the period, with the low- level thermal profile remaining warm and potentially becoming particularly unfavorable for heat impacts around Thursday across coastal, urban, and lower-elevation areas.

AVIATION

(18Z TAFS) Issued at 100 PM AST Sat Oct 3 2026

Afternoon SHRA/TSRA will cont thru 03/21-23Z, with brief impacts possible at TJBQ/TJPS. Trade-wind streamers may affect TJSJ/USVI terminals thru 03/18-19Z. Brief MVFR/IFR CIG/VSBY, lightning, and gusty/VRB winds are possible. E winds 10-15 kt will transition to light/VRB btwn roughly 03/20-21Z and 04/03-04Z, depending on terminal and local influences. Passing SHRA/VCSH will remain possible overnight into the morning, with winds increasing again aft 04/12-14Z from the ESE at 10-15 kt.

MARINE

Issued at 100 PM AST Sat Oct 3 2026

Generally favorable marine conditions are expected across most of the regional waters under a typical easterly trade wind pattern, though locally choppy conditions will persist through tonight across some of the more exposed waters and passages. Winds and seas will gradually ease Sunday into early next week, resulting in more favorable conditions for small craft. Afternoon thunderstorms affecting the western and northern coastal waters may produce locally hazardous marine conditions, including gusty winds, higher seas, and frequent lightning.

BEACH FORECAST

Issued at 100 PM AST Sat Oct 3 2026

A moderate risk of rip currents will continue through Sunday, mainly along the north- and east-facing beaches of Puerto Rico, Culebra, Vieques, and portions of the U.S. Virgin Islands. A brief improvement is expected Monday, with a low risk across most beaches, before moderate rip current conditions return Tuesday along many north- and east-facing beaches.

Thunderstorms developing near the western and northern coastal areas during the afternoon may also produce locally hazardous beach conditions, including frequent lightning. Increasing heat will be another concern Sunday into Monday, especially along exposed coastal areas during the late morning and early afternoon. Beachgoers should continue to check the latest forecast before heading to the beach, as conditions may change from day to day.

SJU WATCHES/WARNINGS/ADVISORIES

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