textproduct: San Juan

KEY MESSAGES

Updated at 300 AM AST Mon Apr 6 2026

* Flooding risk increases this week, highest through midweek. Afternoon and nighttime showers and thunderstorms may produce urban and small stream flooding, with isolated flash flooding possible across Puerto Rico and the US Virgin Islands.

* Life-threatening rip currents continue through this evening. High risk along north and east-facing beaches of Puerto Rico, Culebra, and St. Croix. Risk lowers on Tuesday, then increases again to high by Wednesday afternoon onward.

* Hazardous marine conditions continue for small craft. Small Craft Advisory remains in effect for Atlantic offshore waters and the Anegada Passage through at least this afternoon. Elsewhere, mariners should exercise caution.

* Breezy to locally windy conditions will persist. Winds will enhance shower activity and create hazardous marine and coastal conditions.

* Above-normal heat index values return Tuesday through Thursday. Elevated heat indices will increase the risk of heat- related impacts, especially for sensitive individuals outdoors without adequate hydration or cooling.

Short Term(Today through Wednesday)

Issued at 300 AM AST Mon Apr 6 2026

Under an east-southeast wind flow, showers moved inland across the windward areas of south and east PR, Vieques, Culebra, and the US Virgin Islands, producing ponding in poorly drained areas. However, heavy rain impacted the island of Vieques, where rainfall accumulations ranged from 1 to 2 inches, according to Radar estimates. Rain activity moved further inland across portions of the eastern interior and northern PR during early morning. Additionally, a cluster of strong thunderstorms was noted between the coastal sites of northeast PR, Vieques, and Culebra, and over the Atlantic Offshore waters. Winds across leeward locations were calm to light and variable, while across the windward sites ranged between 5 and 15 mph out from the east-southeast.

A strong surface high pressure extending from the western to central Atlantic will promote breezy to windy east-southeast winds across the northeast Caribbean through the short-term period, as 925 mb climatology suggests values will range near to above normal. Additionally, a series of short-wave troughs at mid to upper-level and a jet streak will promote a somewhat unstable atmosphere today. These features, combined with above-normal Total Precipitable Water, local and/or orographic effects, and sea breeze variations, will likely result in showers and thunderstorms as early as around noon and are more likely by the afternoon. Another round of showers and possible thunderstorms will impact the US Virgin Islands and the southeast or the eastern third of PR from late this afternoon into the evening hours. Under this weather pattern, we have forecast a limited to elevated risk of flooding for portions of the islands during this period. Another threat associated with this pattern is lightning and thunderstorm winds.

The rest of the short term will remain unstable and wet as model vs local climatology suggest, above normal moisture content, with relatively steep lapse rates at mid and low levels, 250 mb heights suggesting the presence of short wave troughs or an amplifying trough, and cooler-than-normal temperatures at 500 mb, which are favorable conditions for organized convection across the region. Additionally, the winds will remain above normal through the short term, and the 925 mb temperatures are expected to show a warmer- than-normal trend, according to model guidance. Although we expect periods with little or no rain, rounds of moderate to locally heavy rain will impact portions of the islands each day, especially across the USVI and PR's windward locations overnight and in the morning, and across the western and northern portions of PR in the afternoon.

Under the aforementioned weather pattern, the weather threats for Tuesday and Wednesday are warm to locally hot heat index during the afternoon, a limited to elevated risk of flooding rain across portions of PR and the USVI, breezy to locally windy conditions, moderate to high risk of life-threatening rip currents, and dangerous lightning near thunderstorm activity.

Long Term(Thursday through Monday)

Issued at 300 AM AST Mon Apr 6 2026

A gradual transition toward a slightly more stable pattern is now expected to begin earlier than indicated in previous model cycles, particularly starting Thursday. Mid-level moisture is forecast to decrease, with 700500 mb relative humidity values dropping closer to near-normal levels. While the overall pattern will remain somewhat moist, this trend suggests a modest reduction in the depth of available moisture compared to earlier in the week.

Despite this drying trend, a generally unsettled pattern will persist. Residual troughing aloft and lingering moisture will continue to support periods of cloudiness and shower activity, especially during the afternoon hours due to diurnal heating and local effects. However, coverage and intensity of convection should be somewhat lower than in previous days. Winds will remain from the east-southeast, continuing to advect moisture into the region, although not as efficiently as earlier in the week. Saturated soils and elevated streamflows from rainfall earlier in the week will continue to support an elevated flooding risk, although more localized in nature, particularly across interior and western Puerto Rico during the afternoon hours.

By Friday into Saturday, conditions are expected to become relatively more stable, with mid-level drying limiting vertical development of convection. This should result in more isolated to scattered shower activity, primarily over western and interior Puerto Rico during the afternoon, with more limited impacts elsewhere.

By the end of the forecast period and beyond, model guidance suggests a return to a wetter and more unstable pattern as another deep-layered trough approaches the region and combines with well- above-normal moisture. However, this portion of the forecast remains in the longer range and carries higher uncertainty. Stay tuned for further updates as confidence improves.

AVIATION

(06Z TAFS) Issued at 300 AM AST Mon Apr 6 2026

VFR conds are expected at local terminals, but MVFR/brief IFR may occur due to passing rain SHRA/TSRA. Eastern terminals like TJSJ, TIST, and TISX will experience SHRA/+SHRA, especially in the morning and evening. Afternoon convection will mainly affect interior, W/N PR, impacting JBQ/JSJ. Winds will be from the ESE at 5-12 kt thru 06/13Z, then at 10-20 kt, with higher gusts near convection and due to sea breeze. Expect mountain obscuration, reduced visibility in heavy rain, and isolated lightning.

MARINE

Issued at 300 AM AST Mon Apr 6 2026

Hazardous marine conditions will persist through at least tonight as a strong high-pressure system over the Atlantic maintains moderate to fresh southeasterly winds. Therefore, expect confused seas particularly across Atlantic waters and local passages throughout the day. Conditions are expected to improve starting early Tuesday morning, with seas subsiding to around 5 feet in the Atlantic and up to 4 feet in the Caribbean. While trade wind showers continue to drift across the region, isolated to scattered thunderstorms are likely this afternoon, especially over coastal waters near western, northern, and northwestern Puerto Rico. Expect shower and thunderstorm coverage to increase slightly later this week as a series of troughs interacts with deep tropical moisture.

BEACH FORECAST

Issued at 300 AM AST Mon Apr 6 2026

A high risk of rip currents remains in effect through this afternoon for the northern and eastern coasts of Puerto Rico, Culebra, and St Croix. Life-threatening conditions are present, with breaking waves around 6 feet along northern shorelines due to a fading northeasterly swell and breezy conditions. While conditions will gradually improve this evening through Tuesday, lowering the risk to moderate, another arriving swell will cause conditions to deteriorate again later this week. Beachgoers, especially inexperienced swimmers, are strongly urged to stay out of the water, avoid areas near rocks or jetties, and follow all posted warnings and lifeguard instructions.

Additionally, passing showers and isolated afternoon thunderstorms may produce gusty winds and brief heavy rainfall, particularly along the northern and western coast of Puerto Rico. Remember: if you hear thunder, seek shelter immediately. For location specific details, please visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through this afternoon for PRZ001-002-005- 008-012.

VI...High Rip Current Risk through this afternoon for VIZ002.

AM...Small Craft Advisory until midnight AST tonight for AMZ711.

Small Craft Advisory until 6 AM AST early this morning for AMZ712-716-741.

Small Craft Advisory until noon AST today for AMZ723.