textproduct: San Juan

KEY MESSAGES

Issued at 156 PM AST Sat Aug 29 2026

- The Heat Advisory remains in effect through 5 PM AST. A brief relief is expected Sunday into Monday before hazardous heat returns around midweek.

- Unsettled and windier conditions are expected tonight into Monday as moisture associated with the remnants of Tropical Storm Dolly move across the region. Lingering moisture may continue into Tuesday.

- The main hazards will be urban flooding, lightning, and gusty winds, especially tonight into Monday. The potential for isolated flash flooding is lower but cannot be ruled out. Rainfall amounts and the location of the highest totals remain uncertain.

- Marine and coastal conditions will become hazardous Sunday into Monday as winds and seas build. Small Craft Advisory is in effect for the offshore Atlantic waters and Anegada Passage. A high rip current risk statement will be in effect by Sunday.

Short Term(This evening through Monday)

Issued at 156 PM AST Sat Aug 29 2026

Relatively calm and hot conditions prevailed across Puerto Rico and the U.S. Virgin Islands today, with partly cloudy skies and only a few showers, mainly across eastern Puerto Rico. East winds remained around 6 to 18 mph with occasional higher gusts. High temperatures reached the upper 80s to lower 90s across coastal and urban areas, and despite the cloud cover, heat indices exceeded 100 degrees in the most heat-vulnerable areas. A transition to wetter and more unsettled weather is expected tonight as a broad tropical wave, associated with the remnants of Dolly, approaches the islands.

Tonight into Sunday, moisture will increase from east to west, with showers and thunderstorms becoming more frequent first across the U.S. Virgin Islands, then over eastern Puerto Rico and then spreading across the rest of Puerto Rico. Deepening tropical moisture will support periods of heavy rainfall and squally weather. The main hazards will be urban and poor-drainage flooding, lightning, and gusty winds. A limited flooding risk is expected across the U.S. Virgin Islands tonight, expanding into Puerto Rico on Sunday, with the potential for an elevated excessive rainfall risk where repeated rounds of heavy rainfall occur. Ponding of water on roads and flooding of poorly drained and urban areas could make travel hazardous, while stronger showers and thunderstorms may produce brief strong wind gusts and frequent lightning.

Unsettled conditions will continue Sunday night through Monday as deep tropical moisture remains across the region. Additional rounds of showers and thunderstorms could increase runoff and flooding impacts, particularly where heavier rainfall repeatedly affects the same areas. Although the rainfall should provide some relief to ongoing dry conditions, it is not expected to end the drought. Increased clouds and rainfall will also provide temporary relief from the recent heat. Those with outdoor or travel plans Sunday and Monday should be prepared for rapidly changing conditions and monitor forecast updates, particularly regarding the timing and location of the heaviest rainfall.

Long Term(Tuesday through next Friday)

Issued at 156 PM AST Sat Aug 29 2026

Deep tropical moisture trailing from the previous tropical wave (the remnants of Tropical Storm Dolly) will remain in place across the forecast area on Tuesday, with GFS model guidance indicating precipitable water (PWAT) values near the 75th percentile for this time of year. At the surface, a weak disturbance (previous dolly) positioned west of the region over Hispaniola will maintain a south- southeasterly wind flow across the local islands. Under this pattern, an unstable, wet weather pattern will prevail, favoring some widespread showers with isolated thunderstorms across eastern Puerto Rico, including the San Juan metro area in the morning hours followed by afternoon showers along the interior west and northwestern sections. By Wednesday, low-level winds will shift from the east-southeast as surface high pressure anchors over the western Atlantic and another extends across the Central Atlantic. This configuration will bring a more variable moisture regime as pockets of deep moisture alternate with drier air patches, resulting in hot and warm conditions with heat indices that could reach 111 degrees across coastal and urban sections. Although conditions will not be favorable for morning advective showers, localized afternoon convective development is expected over interior and western Puerto Rico.

According to the model guidance today, Thursday is forecast to be the driest day of the long-term period as a drier air mass filters into the region, suppressing, in some way, widespread cloud development and keeping maximum temperatures elevated across coastal areas. On Friday, the surface high over the Central Atlantic will extend further south, enhancing easterly trade winds that will push occasional patches of trade wind moisture across the regional waters. By late Friday into Saturday, global model guidance suggests an increase in moisture associated with another tropical wave approaching the local area. In response to the strengthening surface high pressure over the Central Atlantic, low-level winds will veer slightly to the east-southeast, pulling this deeper moisture field across the CWA. This pattern will increase the potential for organized shower and thunderstorm activity heading into the weekend, with localized urban and small-stream flooding risks returning to the forecast area.

AVIATION

(18Z TAFS) Issued at 156 PM AST Sat Aug 29 2026

Mainly VFR conditions expected early in the forecast period. VCSH developing across W PR through 29/22Z. E winds at 15 to 20 kts turning E to ENE and decreasing 8 to 12 kt overnight. ENE to NE winds at 15-20 knots after 30/13Z. VCTS/SHRA increasing across the USVI terminals after 29/23Z and PR terminals after 30/12Z as a tropical wave moves into the region.

MARINE

Issued at 156 PM AST Sat Aug 29 2026

The remnants of Tropical Storm Dolly, now a strong tropical wave, are expected to move across the local area from tonight through late Sunday. Squally weather, strong gusts, occasional lightning and hazardous seas are expected across most waters. A small craft advisory was issued for the Atlantic waters and the Anegada Passage starting on Sunday.

BEACH FORECAST

Issued at 156 PM AST Sat Aug 29 2026

The increase in winds and swells associated with the remnant of Tropical Storm Dolly will allow the high rip current risk to return across the northern, eastern and southeastern coastal areas of PR as well as Vieques, Culebra and the US Virgin Islands. Beachgoers are urged to remain out of the water due to the expected strong currents and rough surf along unprotected coastlines. In addition, thunderstorms with cloud-to- ground lightning and gusty winds are expected during this period across all islands and coastal waters.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007- 008-010>013.

High Rip Current Risk from Sunday morning through Monday afternoon for PRZ001>003-005-008-012-013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

High Rip Current Risk from Sunday morning through Monday afternoon for VIZ001-002.

AM...Small Craft Advisory from 6 AM Sunday to noon AST Monday for AMZ711.

Small Craft Advisory from 6 AM Sunday to 6 AM AST Monday for AMZ723.