textproduct: San Juan

KEY MESSAGES

Updated at 155 AM AST Mon Apr 20 2026

* Limited flooding risk each afternoon, driven by locally induced convection.

* Isolated thunderstorms possible each afternoon, producing lightning and brief gusty winds.

* Choppy, wind-driven seas, subsiding on Tuesday, then build again Wednesday through Thursday with increasing seas and a northerly swell.

* Moderate rip current risk most days, potentially increasing to high by midweek along north and east-facing beaches.

Short Term(Today through Wednesday)

Issued at 155 AM AST Mon Apr 20 2026

Overnight conditions were notably calm across Puerto Rico and the U.S. Virgin Islands, with mostly clear skies prevailing. Winds remained light and variable, similar to previous nights. Coastal areas observed temperatures in the 70s, while interior locations cooled into the 60s. Only a few brief passing showers were seen over the surrounding waters, with little to no impact over land. Overall, tranquil conditions dominated through the overnight hours.

Looking ahead, a drier and more stable pattern will persist from today through Wednesday, as a surface high pressure system over the North Atlantic prevails, and promotes a generally easterly wind flow. While some low-level moisture will remain in place, it will become increasingly shallow, primarily confined below 700800 mb. Today will feature mostly fair weather conditions, with limited shower activity and minimal impacts.

On Tuesday, winds will weaken and shift from easterly to east-southeasterly during the morning, then trend northeasterly by the afternoon through Wednesday. This evolving wind pattern will help steer locally induced convection toward southwestern and southern Puerto Rico. Despite the drier air mass, sufficient low- level moisture combined with daytime heating will support scattered afternoon showers and isolated thunderstorms, followed by improving conditions in the evening. By Wednesday, similar conditions are expected, with stable weather prevailing and only limited afternoon convection.

Flooding risk will remain generally limited through the period, though localized impacts cannot be ruled out. Brief heavy showers may result in ponding of water on roadways and in poor drainage areas, along with minor urban and small stream floodingparticularly in locations where soils remain saturated from recent rainfall. Some rivers are still running elevated and could respond quickly to additional rainfall. Overall, impacts are expected to be localized and primarily confined to the afternoon hours.

Long Term(Thursday through Monday)

Issued at 155 AM AST Mon Apr 20 2026

A seasonal weather pattern is expected to prevail at the start of the long-term period, with precipitable water values near climatological normals and typical trade wind showers moving across the local waters and windward sectors during the overnight and morning hours. Afternoon convective development will remain possible across interior and western portions of Puerto Rico, aided by daytime heating, local effects, and sea breeze convergence. While widespread rainfall risk is not anticipated early in the period, moderate rainfall may still cause localized ponding in urban and poorly drained areas, especially where showers persist or repeatedly affect the same locations.

By late Thursday into Friday, a gradual increase in available moisture is expected as the remnants of a frontal boundary linger north of the region while low-level winds become more southerly. This evolving pattern will promote warmer temperatures and a more humid air mass across the islands. As a result, shower coverage should become more numerous, with the greatest afternoon activity focused over interior and northern to northwestern Puerto Rico, although passing showers will remain possible elsewhere. Localized urban and small stream flooding will become more likely where stronger showers develop.

From Saturday through Monday, southeasterly to southerly flow is forecast to persist and continue transporting tropical moisture into the northeastern Caribbean. Precipitable water values are expected to rise to above normal levels, supporting a wetter and more unstable pattern. Combined with 925 mb temperatures trending above climatological normal, daytime temperatures will likely rise above seasonal values, particularly across coastal and urban areas of Puerto Rico and the U.S. Virgin Islands. This will result in a gradual increase in heat risk by the end of the period, especially in lower elevations.

In this pattern, periods of locally heavy rainfall and isolated thunderstorms will be possible each afternoon, particularly where sea breeze convergence and local effects combine. Residents and visitors should anticipate warmer and humid conditions, increased potential for ponding of water on roadways, and localized flooding in flood-prone areas through the latter part of the forecast period.

AVIATION

(06Z TAFS) Issued at 155 AM AST Mon Apr 20 2026

Most TAF sites should experience VFR conditions. Periods of brief MVFR with VCTS/SHRA after 20/17Z across TJSJ, TJPS, and TJBQ. Prevailing winds should remain from east around 10 to 15 kts gusts around 25 knots after 20/14Z or near VCTS/SHRA and with sea breeze variations.

MARINE

Issued at 155 AM AST Mon Apr 20 2026

A surface high positioned over the Atlantic is currently generating moderate to locally fresh easterly winds, particularly affecting the offshore Atlantic waters and the local Caribbean passages. This is resulting in moderate to choppy sea conditions. Small Craft Operators Should Exercise Caution in these aforementioned areas. Sea states are anticipated to diminish slightly around Tuesday, subsequently increasing to 6 to 7 feet from mid-week onward, owing to a northerly swell propagating across the Atlantic waters. A series of frontal lows and surface highs will result in winds veering and backing during the week, with more ENE winds by midweek and more ESE winds by the end of the workweek.

BEACH FORECAST

Issued at 155 AM AST Mon Apr 20 2026

A moderate risk of rip currents (life-threatening rip currents are possible in the surf zone) will be present at the north and east facing beaches of Puerto Rico as well as beaches of Vieques, Culebra, and the U.S. Virgin Islands to start the workweek. Beachgoers should remain cautious due to these wind-driven seas. The rip current risk is expected to decrease to low along the beaches of the USVI and Vieques from Tuesday afternoon through early Wednesday as winds lighten. Even if the risk for rip currents is low, life- threatening rip currents often occur in the vicinity of groins, jetties, reefs, and piers. Up to a moderate risk of rip currents is forecast through early Wednesday. However, the risk of rip currents is anticipated to potentially increase to high (life-threatening rip currents are likely in the surf zone) along the northern coastline of Puerto Rico by late Wednesday and Thursday, driven by a northerly swell spreading across the Atlantic waters. Additionally, be weather- aware for afternoon thunderstorms and rapidly changing conditions. If you hear thunder, be prepared to seek shelter immediately. For more information, please visit: weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

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