textproduct: San Juan

KEY MESSAGES

Issued at 248 PM AST Sun May 17 2026

* An upper-level trough approaching the islands today will increase the frequency of showers and isolated thunderstorms, particularly across the interior and western PR. Limited to elevated flooding risk.

* A limited heat risk will continue this upcoming week, heat indices expected near the mid 90s to low 100s across urban and coastal areas.

* Breezy conditions will maintain choppy seas. A Small Craft Advisory is now in effect for the offshore Atlantic waters through at least Monday afternoon.

* A moderate risk of rip currents will persist this week, mainly along the north and east facing beaches of Puerto Rico (southern beaches at times), as well as beaches of Vieques, Culebra, and the U.S. Virgin Islands.

Short Term(This evening through Tuesday)

Issued at 248 PM AST Sun May 17 2026

The morning has featured partly cloudy skies with quick-moving passing showers across windward areas of Puerto Rico. Breezy to windy conditions have been observed at local surface weather stations, with easterly winds around 15 to 20 mph and gusts reaching the upper 20s to lower 30s mph. Daytime highs have generally ranged from the upper 80s to lower 90s across urban and coastal areas and from the upper 70s to lower 80s across higher elevations of the islands. Heat indices have generally ranged from the mid 90s to around 100 to 102 degrees F.

This afternoon, expect scattered to numerous showers and thunderstorms across the northwestern quadrant of Puerto Rico. A Flood Advisory has already been issued for Aguada, Anasco, Las Marias, Moca, Rincon, and San Sebastian until 530 PM AST. Impacts include minor flooding in low-lying and poor drainage areas.

East to east-southeast winds will continue transporting tropical moisture across the islands as surface high pressure over the Atlantic promotes breezy easterly winds, particularly across coastal areas. Moisture levels will remain near climatological normals through most of the short-term period, except on Monday, with localized increases during afternoon convection. An amplifying upper-level trough approaching from the west will slightly enhance instability and support periods of showers and isolated thunderstorms across the region.

Late tonight and early Monday morning, an area of cloudiness and trade wind showers will continue moving across the U.S. Virgin Islands and windward sections of Puerto Rico before drier air filters into the area later in the day. Guidance suggests a gradually drier air mass will enter the region on Monday, with PWAT values falling to near or below 1.5 inches by the afternoon. Although somewhat drier air is expected Monday afternoon, daytime heating, local orographic effects, sea breeze convergence, and upper-level support will still promote scattered convection across interior and western Puerto Rico. Isolated thunderstorms may develop and produce heavy rainfall, resulting in ponding of water on roads and poorly drained areas, as well as localized urban and small stream flooding. Flood advisories may be required in some locations. By Tuesday, moisture levels are expected to return closer to normal, with a similar weather pattern continuing across the area.

925 mb temperature guidance indicates temperatures trending closer to seasonal values early this week. As a result, a limited heat risk will persist through Monday and Tuesday, with heat indices slightly cooler expected compared to recent days.

Long Term(Wednesday through Sunday)

Issued at 455 AM AST Sun May 17 2026

A typical late spring to early summer weather pattern is expected through the long-term period. Broad surface high pressure over the northwestern Atlantic will maintain moderate to fresh east to east- southeasterly winds across the local islands, with occasionally strong winds at times. Winds are expected to strengthen further into next weekend, supporting breezy to locally windy conditions. At mid and upper levels, the area will remain between ridging to the southeast and a lingering trough/low over the western Atlantic, while weak disturbances move around the broader pattern and approach the northeastern Caribbean. This pattern will help support periods of increased instability and more favorable conditions for deeper afternoon convection late in the week and into the holiday weekend.

Patchy moisture embedded within the trade winds will continue to promote passing showers during the overnight and morning hours each day, followed by afternoon showers and isolated thunderstorms mainly across interior and western to northwestern areas. Although mid- level conditions may remain somewhat marginal at times, the combination of local effects and strong daytime heating should still support deeper convection each afternoon. Flooding concerns are expected to gradually increase and become more locally elevated late in the week and into the holiday weekend, with locally heavy rainfall, ponding of water on roads, and localized urban and small stream flooding possible. Additional hazards will include lightning, heat, and gusty winds, especially as outdoor activity increases during the Memorial Day weekend.

AVIATION

(18Z TAFS) Issued at 248 PM AST Sun May 17 2026

VFR conditions are expected across all TAF terminals, except at TJBQ due to VCTS/TSRA thru ~17/22Z. Breezy to windy conditions from the E to SE becoming more variable overnight at around 5 to 10 kts. VCSH/-SHRA over TIST, TISX, TJSJ are possible aft 18/06Z From 18/14Z, winds are expected to increase again and VCTS/TSRA are possible across TJBQ aft 18/17Z.

MARINE

Issued at 248 PM AST Sun May 17 2026

A broad surface high pressure over the central Atlantic will promote moderate to locally fresh east to east-southeasterly winds across the regional waters through at least today. From late today into early next week, winds will turn more easterly as another surface high pressure builds over the western Atlantic. These breezy conditions will maintain choppy seas, particularly across the offshore and exposed Atlantic and Caribbean waters. A Small Craft Advisory is now in effect for the offshore Atlantic waters through Monday afternoon. Afternoon and early evening isolated thunderstorms can be expected each day across the northwestern waters of Puerto Rico.

BEACH FORECAST

Issued at 248 PM AST Sun May 17 2026

A moderate risk of life-threatening rip currents will continue to prevail across the east, north, and southern beaches of Puerto Rico, Culebra, Vieques and the U.S. Virgin Islands during the next several days. Beachgoers should exercise caution when entering these beaches. This means life-threatening rip currents are possible in the surf zones, and beachgoers should exercise caution when entering these beaches.

If you become caught in a rip current, yell for help. Remain calm, do not exhaust yourself and stay afloat while waiting for help. If you have to swim out of a rip current, swim parallel to shore and back toward the beach when possible. Do not attempt to swim directly against a rip current as you will tire quickly. For additional information and location-specific rip current details, visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...Small Craft Advisory until 6 PM AST Monday for AMZ711.