textproduct: San Juan

KEY MESSAGES

Issued at 310 AM AST Mon Nov 2 2026

- Periods of warmer conditions will prevail across the islands, Therefore, we urge people to continue to follow heat safety measurements.

- Showers and isolated thunderstorms will affect western to northwestern Puerto Rico, increasing lightning and flooding potential, particularly during the afternoon hours.

- Passing showers will affect eastern PR and the US Virgin Islands, particularly overnight, with mainly ponding of water over roadways and poorly drained areas.

- Weather conditions could deteriorate after midweek, please continue to monitor our forecast.

Short Term(Today through Wednesday)

Issued at 310 AM AST Mon Nov 2 2026

Overnight, patches of clouds over the surrounding waters, some extending into eastern Puerto Rico, produced passing showers. However, rainfall accumulations remained below half an inch. Winds were generally light, while temperatures remained in the lower 80s along coastal areas and ranged from the upper 60s to lower 70s across the mountains.

The workweek will begin with a mixture of sunny skies, passing showers, and afternoon thunderstorms across Puerto Rico and the US Virgin Islands. Through Tuesday, low-level moisture will remain high, while somewhat drier air in the mid levels should limit widespread thunderstorm development. However, daytime heating and local effects will support afternoon convection, with the gradual shift from easterly to southeasterly winds favoring shower and thunderstorm development mainly across western and northwestern Puerto Rico. Locally heavy downpours could result in urban and small-stream flooding in these areas, while passing showers will remain possible elsewhere, including the US Virgin Islands, particularly during the morning hours. This wind shift, associated with high pressure moving eastward across the western Atlantic, will also favor warmer-than-normal temperatures for November. Tuesday currently appears to be the warmest day, with highs potentially reaching the lower 90s across some coastal and urban areas. Combined with elevated humidity, brief periods of heat index values meeting heat advisory criteria remain possible. Regardless of whether an advisory is issued, residents are encouraged to follow heat safety recommendations, particularly those working or spending extended periods outdoors.

By Wednesday, a developing low-pressure system could further weaken local winds and promote a more southerly flow, drawing additional tropical moisture into the region. This may increase shower and thunderstorm activity, while lighter steering winds could allow heavy downpours to linger over the same areas. Meanwhile, a front boundary associated to the low pressure system will approach from the north influencing the distribution of rainfall through the latter half of the week. This evolving pattern could increase the risk of localized flooding across different portions of the island as the week progresses. However, the timing, location, and extent of the heaviest rainfall will depend on how these weather features evolve.At this time, Wednesday appears to be the transition day toward a gradually wetter and more humid weather pattern, with increasing moisture expected to favor greater shower and thunderstorm activity through the latter half of the week.

Overall, residents should remain alert for changing weather conditions, particularly during afternoon commutes and outdoor activities. Avoid driving through flooded roads, take precautions against excessive heat, and monitor forecast updates as rainfall potential increases toward midweek.

Long Term(Thursday through Monday)

Issued at 310 AM AST Mon Nov 2 2026

A more unstable pattern could unfold or continue during the long term period, particularly from Thursday through Saturday. A moist environment will be present, with precipitable water around 2.0 to 2.3 inches, which is considered above normal values based on November climatology (75th percentile). The 850 to 700 mb relative humidity remains high, generally between 75 to 90%, while the 700 to 500 mb layer also shows an increase in moisture, reaching around 70 to 80% by Friday into Saturday. Overall, the moisture profile suggests a deep and relatively moist atmospheric column through this period, supporting favorable conditions for precipitation.

At the synoptic level, an upper-level low, along with its associated surface low and frontal boundary, will move northward across the Atlantic waters during the period (the most unstable part will remain north of the eastern Caribbean). However, this evolution will favor southerly to southwesterly low-level winds, allowing tropical moisture to be transported to our region, as the features move farther north. Light winds will generally prevail across the local area, contributing to weak steering flow and potentially slow moving showers, allowing showers to move slowly and increasing rainfall accumulations, mainly across southern, interior, and northern portions of Puerto Rico, as well as the U.S. Virgin Islands. As a result, flooding will remain one of the main concerns (Level 2 of 4), indicating the potential for flooding in urban areas, along roads, and near small streams and washes. Additionally, isolated flash flooding cannot be ruled out. Other factors to consider are the NCICS forecasts, including the 200-hPa Velocity Potential and Outgoing Longwave Radiation (OLR), which suggest upper-level divergence. There are also signals of equatorial Rossby and Kelvin waves across the Caribbean during this period, which could enhance rainfall activity. Continue to monitor the forecast as confidence increases and updated model guidance becomes available.

By Sunday and Monday, global models agree that a mid to upper level ridge will build bringing a more stable pattern. In terms of moisture content, model differences become more apparent. The GFS maintains higher moisture, particularly in precipitable water and the 850 to 700 mb relative humidity, suggesting that a greater amount of moisture remains available in the atmospheric column. In contrast, the ECMWF indicates more reduction in moisture, with lower precipitable water values and a drier low to mid-level profile. This disagreement introduces some uncertainty regarding the extent of moisture available during this period. Isolated to scattered afternoon showers may still develop across portions of the islands due to daytime heating and local effects, but rainfall coverage and intensity should decrease those days, reducing the flood concerns.

AVIATION

(06Z TAFS) Issued at 310 AM AST Mon Nov 2 2026

VFR conditions across all TAF sites. However, brief period of MVFR conds possible with SHRA and TSRA, occasionally reaching TJBQ after 17Z. Winds will become more SE around 12-15 kts, with stronger gusts near the heaviest thunderstorms activity.

MARINE

Issued at 310 AM AST Mon Nov 2 2026

A surface high over the Western Atlantic and a low pressure over the Central Caribbean will tighten the local pressure gradient and result in more moderate easterly winds and seas building to between 3 and 5 feet, occasionally 6 feet, across the regional waters and passages through tomorrow, Tuesday. By Wednesday onwards, the local pressure gradient will weaken as a low is forecast to develop over the western Atlantic, and winds will be more light to moderate from the south-southeast (gradually veering to become more south- southwest as the workweek continues). Passing showers and isolated thunderstorms will continue across the regional waters over the next few days (possibly becoming more widespread later in the workweek), with locally higher winds and seas near thunderstorms; small craft should exercise caution.

BEACH FORECAST

Issued at 310 AM AST Mon Nov 2 2026

There is a moderate risk of rip currents (life-threatening rip currents are possible in the surf zone) across the northern and eastern-exposed beaches of Puerto Rico, including Culebra and Vieques, and the U.S. Virgin Islands. A low risk of rip currents will continue today across mainly the southern beaches. However, life-threatening rip currents can often occur near jetties, groins, piers, and reefs. Although with some variation, a similar pattern should persist through the workweek with up to a moderate risk. Showers and t-storms are forecast each afternoon, pariculalry near coastal areas of western/northwestern Puerto Rico (possibly becoming more widespread later in the workweek), without ruling out the San Juan Metro Area and the U.S. Virgin Islands.

SJU WATCHES/WARNINGS/ADVISORIES

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