textproduct: San Juan

KEY MESSAGES

Updated at 159 AM AST Fri May 1 2026

* Another day with showers and thunderstorms across the interior and northwestern Puerto Rico is expected, particularly during the afternoon hours. An elevated flooding risk is expected for these areas as these conditions may cause urban and small stream flooding. Saturated soils and elevated river levels may worsen impacts on vulnerable areas.

* Across the U.S. Virgin Islands, mainly fair weather conditions will prevail with a few passing showers moving into the area from time to time.

* Drier and stable conditions are expected to begin to filter into the region later tonight into the weekend, with limited shower activity.

* Warmer-than-normal temperatures will continue through the weekend, with heat indices reaching or exceeding 100F across urban and coastal areas.

Short Term(Today through Sunday)

Issued at 159 AM AST Fri May 1 2026

Overall, weather conditions remained calm during the overnight hours, with a few showers moving into the southern coast of Puerto Rico, Vieques, Culebra, and the northern U.S. Virgin Islands. Elsewhere, fair weather prevailed under mostly cloudy skies. Doppler radar and satellite imagery detected isolated to scattered showers across regional waters with no significant impacts. Overnight minimum temperatures ranged from the mid-70s in coastal and urban areas to the low-to-mid 60s across the mountains, with light and variable winds at 5 knots or less.

Abundant moisture persists across the region today, with precipitable water (PWAT) values around 2.00 inches. Combined with daytime heating and local effects, afternoon convective activity is likely once again. This could produce showers and isolated thunderstorms, particularly across the interior and northwestern portions of Puerto Rico. Because winds remain light, slow-moving showers may enhance the flooding potential; therefore, the risk of flooding remains elevated for localized portions of northwestern Puerto Rico. Given that soils are already saturated from previous rainfall, rapid river rises and isolated landslides cannot be ruled out. Across the U.S. Virgin Islands, conditions will stay relatively stable, with only passing morning showers and minimal impacts throughout the day.

A gradual decrease in moisture is expected to begin tonight and continue into the weekend, with PWAT values dropping to between 1.30 and 1.60 inches. This drying trend will be supported by the arrival of a drier air mass and a surface high-pressure system strengthening over the central Atlantic. This setup will promote light to moderate southeasterly winds through early next week, while a mid-level ridge provides stability aloft. Although drier and stable conditions are anticipated this weekend, daytime heating and local effects could still trigger a few localized showers across northwestern Puerto Rico.

As the weekend approaches and drier air filters in, temperatures are expected to rise. Warm to hot conditions will persist, especially across coastal and urban areas, where daily maximums will reach the upper 80s to low 90s. In higher elevations, temperatures will range from the upper 70s to mid-80s. Heat indices are forecast to reach or exceed 100F each day. Residents and visitors are urged to stay hydrated and take frequent breaks in shaded or air-conditioned areas to mitigate the risk of heat-related illness.

Long Term(Monday through Friday)

Issued at 159 AM AST Fri May 1 2026

The long-term period will be mainly dominated by generally tranquil, near-seasonal conditions across both Puerto Rico and the U.S. Virgin Islands. Surface high pressure over the central Atlantic will promote east to southeast winds at 8 to 15 mph throughout the period. Aloft, a ridging pattern will persist through Wednesday, supporting stable conditions. As mentioned in previous discussions, the driest period is expected from Monday through Wednesday. A drying trend will lead to improving conditions. Model guidance has been somewhat variable over the past few days, previously indicating below-normal moisture content and now suggesting near-normal values. Nevertheless, PWAT values are expected to remain lower, around 1.5 inches or less. Combined with a mid to upper-level ridge, this will enhance atmospheric stability. Afternoon showers may still develop due to local effects and diurnal heating; however, coverage will be limited and activity brief. Rain chances will range from 10 to 40 percent each afternoon across northwestern Puerto Rico.

By Thursday, moisture will increase back to near-normal levels as patches of moisture move into the region. At the same time, an upper- level trough will begin to amplify, briefly increasing instability and the potential for shower development. However, the latest GFS and ECMWF runs indicate that the trough will quickly move away, allowing ridging to reestablish itself in the mid to upper levels as early as Friday.

At 925 mb, temperature guidance continues to indicate above-normal values (around the 75th percentile) for this time of year. Combined with a prevailing east to southeasterly wind flow, warm conditions will persist throughout the forecast period. Daytime highs will range from the upper 80s to low 90s in coastal and urban areas, and from the upper 70s to mid-80s in higher elevations. Heat indices will reach the upper 90s to low 100s degrees F each day. A limited heat threat will persist across urban, coastal, and low-elevation areas. Residents and visitors should stay hydrated and limit prolonged sun exposure during peak heating hours.

As a result, generally sunny and warm days will prevail, with some light, wind-driven showers overnight and during the early morning hours in windward areas, along with limited afternoon convection across northwestern Puerto Rico. Thursday will have the best chances for rainfall, but overall, minimal impacts are expected.

AVIATION

(06Z TAFS) Issued at 159 AM AST Fri May 1 2026

Mainly VFR conditions will likely continue across most TAF sites. However, SHRA/TSRA expected to develop over the interior and northwestern Puerto Rico in the afternoon hours. This activity will result in brief MVFR/IFR conditions with VCTS for TJPS and TJBQ through 01/22-23Z. Winds will be light and variable early this morning, becoming SE between 8-12 kt after 01/14Z. Winds will return to light and variable by 01/23Z through 02/14Z.

MARINE

Issued at 159 AM AST Fri May 1 2026

A broad surface high over the central Atlantic interacting with lower pressure and a weak trough near the region will maintain an east to east-southeasterly flow across the local waters through the weekend. Winds will increase from 515 knots today to 1020 knots with higher gusts through Saturday night and Sunday. Seas will generally range from 3 to 5 feet, occasionally up to 6 feet, driven by a combination of local wind waves and a small, long-period northerly swell moving through the Atlantic waters and passages. Scattered showers and isolated thunderstorms associated with the nearby trough and moisture will continue at times, producing locally higher winds and seas. Conditions will gradually improve early next week as the pressure gradient relaxes and seas subside.

BEACH FORECAST

Issued at 159 AM AST Fri May 1 2026

A moderate risk of rip currents will persist across north- and east- facing beaches of Puerto Rico, including Culebra, and across all of the U.S. Virgin Islands. A small, long-period northeasterly swell continues to move through the local waters, supporting breaking waves around 3 to 5 feet along exposed beaches. Another weak northerly swell arriving by Saturday will maintain this pattern. No significant changes are expected in the beach forecast, but life- threatening rip currents remain possible and beachgoers should exercise caution.

For additional information, visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

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