textproduct: San Juan

KEY MESSAGES

Issued at 200 AM AST Wed Nov 4 2026

- Another day with warm and humid conditions, particularly across urban and low-lying areas of the islands. Therefore, the Heat Advisory remains in effect from 10 AM through 4 PM AST.

- Showers and thunderstorms are expected across the interior extending to northwards Puerto Rico, leading to ponding of water over roadways and minor flooding.

- A wetter pattern is expected from Thursday through Saturday. Increasing moisture and slow-moving showers and thunderstorms could raise the flooding threat, including urban and small- stream flooding, with isolated flash flooding possible, as well as landslides.

- Another swell is forecast to arrive this Friday into the weekend, bringing hazardous seas and life-threatening rip currents. Refer to the Beach Forecast section for additional details.

Short Term(Today through Friday)

Issued at 200 AM AST Wed Nov 4 2026

Partly cloudy skies prevailed across Puerto Rico and the US Virgin Islands overnight, with a few showers reaching the eastern municipalities of Puerto Rico. Winds remained light and variable, while temperatures generally ranged from the upper 70s to lower 80s across urban and coastal areas, and from the upper 60s to 70s across the higher terrain.

Another hot day is expected across Puerto Rico and the US Virgin Islands today, with a Heat Advisory in effect from 10 AM through 4 PM AST. Abundant surface moisture and increasingly southerly winds will contribute to heat indices ranging from 100 to 108 degrees Fahrenheit, particularly across urban and coastal areas, while minor concentrations of Saharan dust may result in hazy skies. Residents and visitors are urged to stay hydrated, limit prolonged sun exposure, and follow health officials recommendations to reduce the risk of heat exhaustion and heat stroke. Meanwhile, as a surface low continues to develop along a frontal boundary north of the region, additional tropical moisture will spread across the islands, with precipitable water values increasing to around 2.02.2 inches today. By the afternoon, increasing moisture, daytime heating, and local effects will support scattered to numerous showers and thunderstorms. Given the light winds, showers and thunderstorms are expected to develop initially along the Cordillera Central before spreading into other portions of Puerto Rico. Some thunderstorms could produce heavy rainfall, frequent lightning, and gusty winds, with slow movement increasing the potential for urban and small-stream flooding.

Conditions will become increasingly favorable for widespread and locally deep convection Thursday as deeper tropical moisture spreads across the region. Both the GFS and ECMWF indicate increasing mid level relative humidity and precipitable water values to around 2.3 inches. As surface winds become more southerly to southwesterly, enhanced moisture transport and convergence will favor showers and isolated thunderstorms over the surrounding waters and coastal areas during the morning, followed by numerous to widespread afternoon showers and thunderstorms, particularly across the interior, northern and eastern sections of Puerto Rico. This unsettled pattern is expected to continue into Friday, with additional rainfall potentially exacerbating conditions in areas affected previous days. Thursday remains the favored day for the most widespread and heaviest rainfall, although the exact distribution and magnitude will depend on the evolution. Therefore, the risk of urban and small-stream flooding, localized flash flooding, and landslides in steep terrain will increase, potentially resulting in flooded roadways and rapid rises along streams and rivers. Residents and visitors, particularly those in flood-prone and landslide-prone areas, should monitor forecast updates and heed any flood advisories or warnings.

Overall, forecast confidence remains moderate to high in the transition toward a wetter and more convectively active weather pattern through Friday. However, confidence is lower regarding the precise location and timing of the heaviest rainfall. Nevertheless, Thursday and Friday remain the primary periods of concern for excessive rainfall and associated flooding impacts.

Long Term(Saturday through Wednesday)

Issued at 200 AM AST Wed Nov 4 2026

Following the trend of the short term period, by Saturday, atmospheric instability and available moisture will remain elevated. Precipitable water (PWAT) will continue generally above normal (2 inches) as a southwesterly steering flow continues to bring tropical moisture towards the islands. This tropical moisture will continue to move northwards and upper-level trough and its corresponding frontal low. Although the core of maximum instability is still forecast to pass north of the area, this pattern will continue to result in a generally WSW to W surface flow to start the period. 925 mb winds will increase to more seasonal levels on Saturday before decreasing to more light and variable Sunday through at least early Wednesday. Relative humidity from 850 to 700 mb and from 700 to 500 mb should remain at high end normal to above normal values for the month on Saturday. Showers and t-storms are likely to develop to start the period, generating elevated rainfall totals, primarily across the southern, interior, northern and northeastern sectors of Puerto Rico, as well as the U.S. Virgin Islands. This will result in flooding (Risk level 2 of 4) especially across interior, northern and northeastern Puerto Rico during the afternoon hours with these showers and t-storms possibly moving east towards Vieques, Culebra and the northern USVI.

With the upper trough and frontal low moving away from the area, a transition to a more stable pattern with mid-to-upper level riding is forecast Sunday through Wednesday. Models are in more agreement in terms of moisture availability than in the past few days. PWAT and RH values are forecast to fluctuate between normal to above normal values during that period, with a sharper decrease towards more normal values Tuesday into Wednesday. As mentioned above, 925 mb wind speeds will be on a decreasing trend Sunday onwards before gradually increasing once again towards Wednesday. These lighter and variable surface winds will gradually pick up from the ESE and then E to end the period, albeit under a more southerly steering flow. Although daytime heating and localized effects may still generate scattered afternoon convection across the islands, a general decrease in shower activity and intensity is expected when compared to the short term period and Saturday, reducing the flood threat. 925 mb wind speeds are still forecast at above normal values for most of the period. Please stay tuned for subsequent updates as the forecast evolves.

AVIATION

(06Z TAFS) Issued at 200 AM AST Wed Nov 4 2026

VFR conditions across all TAF sites. However, SHRA/TSRA over the interior and northern PR may cause tempo MVFR conds at TJPS, TJBQ, and TJSJ through 04/22Z. Mostly VCSH expected across the rest of the PR and USVI terminals. HZ due to suspended Saharan dust is expected through late today, but VSBY should remain P6SM. Winds will remain light from SE, with higher gust near the heaviest afternoon shower activity.

MARINE

Issued at 200 AM AST Wed Nov 4 2026

A developing low-pressure system north of Puerto Rico will weaken the local pressure gradient Wednesday through Friday, resulting in generally light winds shifting from southeast to south and southwest, with periods of variable winds. Showers and thunderstorms will increase across the regional waters, particularly Thursday and Friday, producing locally gusty winds, reduced visibility, and lightning. Seas will initially subside before a north-northwesterly swell arrives Friday and builds through the weekend, creating increasingly hazardous conditions for small craft across the Atlantic waters and exposed passages. Swell effects could persist into Monday, with another pulse of northeasterly swells arriving.

BEACH FORECAST

Issued at 200 AM AST Wed Nov 4 2026

A moderate risk of rip currents will persist along north- and east- facing beaches of Puerto Rico and portions of Culebra and the northern U.S. Virgin Islands Wednesday through at least Friday. A north-northwesterly swell arriving Friday will build through the weekend, increasing surf and bringing a high risk of life- threatening rip currents to exposed northern beaches Saturday and Sunday and possibly early next week. A moderate risk will extend to additional beaches, including portions of Vieques and St. Croix.

Thunderstorms will pose an additional hazard to beachgoers, with isolated to scattered thunderstorms possible Wednesday and isolated thunderstorms Thursday through Sunday. Beachgoers should leave the water and seek shelter in a substantial building when they hear thunder. Avoid swimming at beaches under a high rip current risk.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for PRZ001>013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for VIZ001-002.

AM...None.