textproduct: San Juan

KEY MESSAGES

Issued at 155 PM AST Sun Oct 25 2026

- A Heat Advisory remains in effect until 5 PM AST this afternoon for Puerto Rico and the U.S. Virgin Islands. Hot and humid conditions will increase the risk of heat-related illnesses, especially across urban and low-lying areas or with prolonged outdoor activity.

- Life-threatening rip currents will impact exposed northern, northwestern, and eastern beaches of Puerto Rico and Culebra, where a High Rip Current Risk remains in effect through Tuesday afternoon. A moderate rip current risk persists for Vieques and the U.S. Virgin Islands.

- Relatively drier conditions will persist across Puerto Rico and the U.S. Virgin Islands over the next few days. However, pockets of low- level moisture will produce passing showers, primarily over southern and southeastern Puerto Rico during the afternoon and overnight hours.

Short Term(This evening through Tuesday)

Issued at 155 PM AST Sun Oct 25 2026

The morning was tranquil across Puerto Rico and the U.S. Virgin Islands, with little to no rainfall reported. Satellite imagery showed mostly clear to partly cloudy skies across the region, with high clouds streaming from west to east. The 12Z TJSJ sounding indicated a precipitable water (PWAT) value of 1.72 inches, lower than yesterday, with mean low-level winds from the southeast at 10 to 13 kt. Plenty of drier air was observed between 850 and 200 mb, limiting shower activity. The main hazard today has been the heat. Under southeasterly flow, maximum temperatures reached the upper 80s to lower 90s across the lowlands, urban areas, and coastal sections of Puerto Rico and the U.S. Virgin Islands, with elevated heat indices mainly across coastal and urban areas. A Heat Advisory remains in effect until 5 PM AST for all of Puerto Rico and the U.S. Virgin Islands. Residents and visitors are advised to stay hydrated and avoid prolonged exposure to the sun. Additionally, continue to monitor forecasts and alerts, as additional heat-related products may be issued over the coming days. Temperatures at 925 mb are expected to remain above normal, combined with sufficient moisture at the surface and southeasterly wind flow.

The overall pattern remains on track, with a mid to upper-level trough over the western Caribbean and a ridge aloft over the eastern Caribbean, along with southeasterly surface flow. Based on the latest model guidance, the remainder of the afternoon will feature warm to hot conditions and a few shallow passing showers driven by local effects across northwestern Puerto Rico. No significant flooding concerns are expected, as any showers should move quickly. From tonight into Monday, guidance suggests that an area of increased moisture, with PWAT values near 2 inches, will move into the Caribbean waters and could bring periods of persistent passing showers. The highest chance of observing this activity will be across southeastern and southern Puerto Rico during the overnight hours, where ponding of water on roads and in poorly drained areas will be possible.

Both GFS and ECMWF guidance indicate decreasing moisture levels and warming temperatures aloft. Despite these trends, moisture in the low levels may support passing showers and isolated afternoon thunderstorms. Forecast confidence decreases on Tuesday, as the GFS indicates a return to PWAT values near 2.0 inches, while the ECMWF maintains a drier environment, with values decreasing into the 25th percentile. Continue to monitor the forecast as adjustments and updates become available.

Long Term(Wednesday through next Saturday)

Issued at 421 AM AST Sun Oct 25 2026

Fair weather conditions should continue over the second part of the workweek, becoming wetter and unstable by the weekend. A surface high pressure over the central Atlantic should continue to maintain a SE-S wind flow through most of the forecast period. However, the steering flow should remain weak as the surface high interacts with a deep-layered trough deepening into the tropics, weakening the local pressure gradient.

Aloft, global model solutions continue to suggest a ridge in the central Atlantic interacting with the trough, though the ridge should continue to dominate the weather pattern on Wednesday and Thursday. During this period, guidance suggests a drop in moisture content across the CWA, with PWAT values below climatological normal (below 1.75 inches), as a dry slot filter in the low and mid levels. Additionally, the vicinity of the ridge will likely maintain warmer-than-normal mid level temperatures (above 6 C), leading to subsidence and stability aloft.

According to the latest CFS forecast, the CWA may be under a suppressing area, disfavoring deep convection. Although daytime heating and local effects will drive the afternoon convection, showers and isolated thunderstorms over the mountain ranges of Puerto Rico may not produce significant rainfall, lowering the flood chance. Friday onwards, the weather conditions may become wetter and unstable as the deep- layered trough and a TUTT approaches the local area, cooling mid level temperatures (between -6 and -8 C), with steeper mid-level lapse rates, increasing instability aloft. Additionally, CFS forecasts the MJO across the local area, enhancing upward motion and favoring deeper convection. Additionally, PWAT values should reach above-normal values (up to 2.25 inches), reflected in both low and mid levels, reflected in the latest deterministic guidance of the GFS and ECMWF.

Additional to afternoon convection across Puerto Rico, showers and isolated thunderstorms may move across windward sections of Puerto Rico and the U.S. Virgin Islands during the night and morning hours, followed by afternoon convection across the mountain ranges of Puerto Rico. Due to low steering winds, showers and thunderstorms may linger longer than usual, increasing rainfall accumulations over the aforementioned areas. Therefore, the flood threat will remain elevated on Friday and Saturday, with mainly urban and small stream flooding, along with rapid river rises. Thunderstorms may produce gusty winds and frequent lightning.

AVIATION

(18Z TAFS) Issued at 155 PM AST Sun Oct 25 2026

Mainly VFR conditions thru the forecast period. Afternoon shallow convection may produce brief MVFR conditions and mountain obs across TJBQ. Additional VCSH & SHRA will affect southern and eastern terminals tonight into early Monday. SE winds around 10 to 15 kt will prevail, with sea breeze variations and gusts up to 20 kt, becoming 10 kt or less overnight.

MARINE

Issued at 155 PM AST Sun Oct 25 2026

Surface high pressure across the central Atlantic will maintain moderate to locally fresh southeasterly winds across the region through at least Tuesday. Choppy seas will persist across the Atlantic waters and the Mona Passage through the next few days. A long-period northerly swell will spread across the Atlantic waters and local passages by Monday, building seas up to around 7 feet and maintaining hazardous marine conditions through at least Tuesday.

BEACH FORECAST

Issued at 155 PM AST Sun Oct 25 2026

A combination of a subsiding northerly swell and additional long-period northerly swell pulses will generate life-threatening rip currents along north-facing beaches of Puerto Rico and Culebra through mid-week. Consequently, a High Rip Current Risk remains in effect for the northern, western, and eastern beaches of Puerto Rico and Culebra through at least Tuesday night. Beachgoers are strongly urged to stay out of the water in these areas. Always heed posted alerts, flags, and instructions from lifeguards and local officials.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through Tuesday afternoon for PRZ001-002- 005-008-010-012.

Heat Advisory until 5 PM AST this afternoon for PRZ001>013.

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

AM...None.