textproduct: San Juan

KEY MESSAGES

Issued at 221 PM AST Thu Oct 29 2026

- Strong thunderstorms and heavy showers will continue to affect portions of interior, northwestern, and north central Puerto Rico, including parts of the San Juan metro area, through the rest of the afternoon. Urban and small stream flooding, frequent lightning, and gusty winds are possible.

- Hot and humid conditions will continue across Puerto Rico and the U.S. Virgin Islands, particularly during the late morning and afternoon hours. Those sensitive to heat should take precautions.

- Exceptionally high tides will persist through at least Friday, with the highest tide expected late Friday morning. Localized coastal flooding remains possible along vulnerable, low-lying shorelines, even as northerly swell energy subsides.

- Unsettled weather conditions are expected this weekend, with an increasing potential for showers and thunderstorms. Locally heavy rainfall could lead to flooding, particularly in areas with poor drainage and locations that have already received significant rainfall.

Short Term(This evening through Saturday)

Issued at 221 PM AST Thu Oct 29 2026

Today, generally quiet weather conditions prevailed across Puerto Rico and the US Virgin Islands during the morning hours. By early afternoon, showers developed across the San Juan metropolitan area and southeastern Puerto Rico, supported by daytime heating, available moisture, and southeasterly winds. The main concerns with any heavier showers are ponding of water on roads and localized urban flooding, particularly in areas with poor drainage.

Tonight into Friday, a drier air mass moving into the region from the east will gradually limit shower activity. However, passing showers may still affect eastern Puerto Rico and the U.S. Virgin Islands overnight, followed by isolated to scattered afternoon showers across western and northwestern Puerto Rico on Friday due to daytime heating and local effects. Overall, the flooding threat should remain limited, with most areas experiencing relatively quiet weather conditions.

By Saturday, a gradual increase in moisture is expected as a deepening trough over the western Caribbean influences the region. Although some afternoon showers and isolated thunderstorms may develop across interior and western Puerto Rico, the better potential for increased shower coverage appears to be by late Saturday, potentially increasing into Sunday. This trend is supported by both the GFS and ECMWF, which indicate precipitable water values approaching or exceeding 2.0 inches, along with increasing mid level moisture by late Saturday. These conditions could lead to periods of moderate to locally heavy rainfall, increasing the potential for urban and small stream flooding in areas receiving persistent showers. Lightning will also be a concern with any thunderstorm development. Confidence is moderate in the increasing moisture trend, but uncertainty remains regarding the location and intensity of the heaviest rainfall.

Overall, the best day for outdoor activities will be Friday into the first half of Saturday. Above-normal temperatures will persist, so adequate hydration and precautions against heat exposure are recommended. The most active day of the short term period will be late Saturday.

Long Term(Sunday through Thursday)

Issued at 227 AM AST Thu Oct 29 2026

Current model guidance suggests a humid pattern throughout the long term period, favoring unsettled weather conditions and an increased potential for rainfall. Precipitable water (PWAT) values are expected to remain at or above 2 inches beginning Sunday, above normal values based on November climatology (75th percentile). Meanwhile, relative humidity in the 850 to 700 mb layer is expected to remain near seasonal levels, while relative humidity in the 700 to 500 mb layer is forecast to remain above normal.

At the surface, high pressure over the Atlantic will promote easterly to northeasterly winds at the start of the period, gradually becoming southeasterly to southerly early next week. Aloft, an upper level trough is expected to remain primarily west of the region through the beginning of the period. However, some uncertainty remains, as current model guidance suggests that the trough will gradually move away from the region early next week. The upper-level trough, along with embedded shortwave troughs, will support mid-level temperatures near -6C through at least Monday, potentially favoring cloud development and deeper convection across the region. From Tuesday onward, guidance indicates a gradual warming of mid-level temperatures, which could become less favorable for deeper convection. By midweek, winds are expected to become very light, potentially resulting in slow moving showers and increasing the risk of localized flooding. However, confidence in the overall rainfall coverage and intensity remains limited, as upper level dynamics may become less favorable. Afternoon convection will also depend on cloud cover and the amount of daytime heating.

Overall, showers are expected during the overnight and morning hours each day, particularly across the U.S. Virgin Islands and eastern to southeastern Puerto Rico. During the afternoon, convection is expected to develop across the interior, western, and northwestern portions of Puerto Rico, with localized showers and streamers also developing downwind of El Yunque and across the local islands on most days. Periods of heavy rainfall could lead to urban and small stream flooding. In addition, thunderstorms may produce frequent lightning and gusty winds. Continue to monitor the forecast for updates as model guidance becomes more consistent.

At this time, upper level dynamics appear more favorable for enhanced convection on Sunday, at the beginning of the period. Later in the week a mid-level ridge could help inhibit development. But lighter winds could favor localized rainfall accumulation due to the slow movement of showers. Nevertheless, cloud cover will remain an important factor in determining the extent and intensity of afternoon convection. Forecast uncertainty remains, as global models continue to show some disagreement regarding the evolution of the upper level pattern.

AVIATION

(18Z TAFS) Issued at 221 PM AST Thu Oct 29 2026

VFR conds across all terminals. SHRA/TSRA across interior and NW PR thru 22Z may cause mtn obscurations and brief MVFR conds. SE at 8-16 kts and higher gust near the heaviest thunderstorm activity, bcmg lgt/VRB overnight. SE winds becoming E by 30/12Z.

MARINE

Issued at 221 PM AST Thu Oct 29 2026

A surface high-pressure system over the central Atlantic will maintain moderate east to southeasterly winds across the regional waters through the next few days. The long-period northerly swell affecting the local waters will continue to gradually subside through tonight into Friday. Nevertheless, choppy conditions may persist across portions of the offshore waters and local passages. Scattered showers and isolated thunderstorms will remain possible, particularly over the waters north and west of Puerto Rico, resulting in locally gusty winds and brief periods of reduced visibility.

BEACH FORECAST

Issued at 221 PM AST Thu Oct 29 2026

The High Rip Current Risk has expired as the northerly swell continues to gradually subside. However, a moderate risk of rip currents will persist along portions of the north-facing beaches of Puerto Rico and Culebra, as well as across the U.S. Virgin Islands.

Additionally, the ongoing period of exceptionally high tides will continue through at least Friday. Localized coastal flooding will remain possible around the time of high tide, particularly along susceptible low-lying shorelines, with the highest tide expected late Friday morning. Although northerly swell energy continues to diminish, these exceptionally high tides may still exacerbate coastal impacts, including localized water intrusion and minor coastal flooding.

SJU WATCHES/WARNINGS/ADVISORIES

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