textproduct: San Juan

KEY MESSAGES

Updated at 330 AM AST Thu Apr 30 2026

* An elevated flooding risk is expected today for portions of the interior, northern and northwestern Puerto Rico as strong showers and thunderstorms develop during the afternoon hours. Soils are already saturated from previous rains and elevated river levels may worsen impacts in vulnerable areas.

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

* A gradual transition into drier and stable conditions is expected to from late Friday onward, as a high-pressure system strengthens to the north and a mid-level ridge builds over the region.

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

* A moderate rip current risk will continue for north- and east- facing beaches of the islands. Beachgoers should exercise caution along exposed beaches.

Short Term(Today through Saturday)

Issued at 330 AM AST Thu Apr 30 2026

Calm conditions prevailed across the islands overnight; however, Doppler radar and satellite imagery detected persistent shower bands over the offshore Atlantic waters and the Mona Channel, northwest of Aguadilla. While some of these showers brushed the coastline, the rest of the region experienced mostly clear to partly cloudy skies. 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 remaining at 5 knots or less.

Another day of wet and unsettled weather is expected as abundant moisture, with precipitable water (PWAT) values up to 2.25 inches, moves over the islands. With winds remaining light and variable, conditions are favorable for another round of afternoon convective activity across central, northern, and western Puerto Rico, including the San Juan metropolitan area. Moderate to heavy rainfall and thunderstorms are likely across these areas, fueled by daytime heating, local effects, and instability aloft.

Given the slow-moving nature of these storms, the risk of flooding will remain elevated through Friday. Heavy rainfall, frequent lightning, and gusty winds are expected, which may lead to rapid river rises and minor urban flooding. Because soils are already saturated from previous rainfall, landslides cannot be ruled out, particularly across the central municipalities of Puerto Rico. Meanwhile, the U.S. Virgin Islands will likely see only passing morning showers with minimal impacts.

A gradual transition toward drier, more stable conditions is anticipated late Friday into Saturday as a high-pressure system strengthens to the north and a mid-level ridge builds over the region. Warm to hot temperatures will persist throughout the weekend, especially across coastal and urban areas, where heat indices are forecast to reach or exceed 100F each day.

Long Term(Sunday through Thursday)

Issued at 330 AM AST Thu Apr 30 2026

The long-term period will be dominated by generally tranquil, near- seasonal conditions for 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 through the period. Aloft, a ridging pattern will persist, supporting stable conditions. On Sunday, patches of moisture will maintain precipitable water (PWAT) values near seasonal levels, around 1.5 inches. This will support brief, passing showers across windward areas during the morning, followed by scattered afternoon showers and isolated thunderstorms across the northwestern quadrant of Puerto Rico. Flood risk will remain low and localized.

A drying trend will develop early next week, leading to improving conditions. Model guidance indicates PWAT values falling into the 25th percentile. In perspective, PWAT values are expected to be around 1.25 inches or less. Combined with a mid to upper-level ridge, this will enhance stability. The driest period is expected from Monday through Wednesday. Afternoon showers may still develop due to local effects and diurnal heating, but coverage will be limited and activity brief. Rain chances will range from 10 to 30 percent each afternoon across northwestern Puerto Rico. By Thursday, moisture will increase back to near-normal levels as patches of moisture arrive. At the same time, an upper-level trough will begin to amplify into the region, increasing instability and the potential for shower development.

Despite reduced rainfall, the main hazard will be the warm conditions that will likely persist across the islands. Temperature guidance at 925 mb, along with a prevailing east to southeasterly wind flow, suggests values will remain above normal 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 daily. A limited heat threat will persist for urban, coastal, and low-elevation areas. Residents and visitors should stay hydrated and limit prolonged sun exposure during peak heating hours.

AVIATION

(06Z TAFS) Issued at 330 AM AST Thu Apr 30 2026

Mainly VFR conds will likely continue across most TAF sites. Wet and unstable conditions will persist today, bringing rounds of SHRA/TSRA during the aftn hours. This activity will result in brief MVFR/IFR conds with VCTS for TJSJ/TJPS/TJBQ thru 30/23Z. Light/variable winds early in the morning, becoming E-SE btw 8-12 kt after 30/14Z. Winds will turn light/variable by 30/23Z thru 01/14Z.

MARINE

Issued at 330 AM AST Thu Apr 30 2026

A series of highs and frontal lows over the western to central Atlantic will prevail over the next few days. Winds will become more east- southeasterly today and east to east southeasterly on Friday. Moisture over the region and a nearby trough will continue to result in showers and isolated t-storms over the next few days, particularly during the afternoon hours. Pulses of small, long- period northerly swell will continue to spread across the Atlantic waters and local passages through this evening, though seas should remain between 2 to 4 feet. Periods of another weak but long-period northerly swell will reach the Atlantic waters by early Saturday.

BEACH FORECAST

Issued at 330 AM AST Thu Apr 30 2026

The moderate risk of rip currents will continue for north- and east- facing beaches of the Puerto Rico due to pulses of a small, long- period northeasterly swell. Intermittent periods of moderate to low risk of rip current for the rest of the islands. Life-threatening rip currents remain possible in the surf zone. A low risk of rip currents will persist elsewhere, though isolated stronger currents may develop near piers, jetties, reefs, and channels. Beachgoers should exercise caution and monitor the weather, as showers and thunderstorms may affect coastal areas at times through Friday.

For additional information and location-specific rip current details, please visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

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