textproduct: San Juan

KEY MESSAGES

Issued at 138 PM AST Sun Nov 1 2026

- Showers and isolated thunderstorms across interior and western Puerto Rico is forecast this afternoon, increasing lightning and flooding potential.

- Passing showers across the U.S. Virgin Islands and eastern Puerto Rico tonight and early Monday, with mainly ponding of water over roadways and poorly drained areas.

- Warmer conditions this workweek will lead to heat indices exceeding 100 Fahrenheit across urban and low-lying areas of the islands. Stay hydrated.

Short Term(This evening through Tuesday)

Issued at 138 PM AST Sun Nov 1 2026

Mostly sunny to partly cloudy skies were observed across Puerto Rico and the U.S. Virgin Islands this morning. A line of brief, but heavy showers moved over the southeastern municipalities of PR early in the morning hours. High temperatures were from the upper 80s to low 90s across most lower elevations. The wind prevailed from the east between 8 and 14 mph, with sea breeze variations and gusts near 30 mph. For the rest of this afternoon, locally induced streamers will develop downwind of the USVI, producing minor rainfall accumulation in general over land areas. Meanwhile, the combination of daytime heating with the available moisture content (near 2.10 inches of PWAT), and the sea breeze convergence will trigger thunderstorm development over the interior and western PR, which could lead to urban and small-stream flooding.

A similar weather pattern is expected through early Tuesday, as drier mid-level air filters from the east, and limits convection mainly to west/northwest PR due to diurnal and local effects. The flood threat will remain elevated across those areas on both days. Elsewhere, mostly passing trade wind showers are expected at times. Winds are expected to turn more southeast as the surface high over the western Atlantic moves slightly eastward, and a weak low-level low pressure develops over the southwestern Atlantic late in the period. This will also promote warmer than normal temperatures during the day, and heat advisory conditions are possible, particularly on Tuesday. Late in the period, if the synoptic scenario unfolds, the developing low could pull higher moisture content over the region under a deep southerly flow.

Long Term(Wednesday through Sunday)

Issued at 247 AM AST Sun Nov 1 2026

A generally warm and humid weather pattern is expected across Puerto Rico during the long term period. Precipitable water (PWAT) values are expected to remain generally elevated most of the forecast period, ranging between 1.9 and 2.3 inches. Low-level relative humidity (850 to 700 mb) is expected to remain generally between 70% and 85%, while mid-level moisture (700 to 500 mb) will increase considerably from Wednesday through Friday, reaching values near or above the 75th climatological percentile of the month of November. Some drying is then anticipated toward the end of the period, particularly on Sunday, as drier air filters into the region. Meanwhile, 500 mb temperatures around -5 to -6C will contribute to some atmospheric instability, particularly during periods of stronger daytime heating. 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. This evolution will favor southerly low-level winds, allowing tropical moisture to be transported toward the region, particularly on Saturday as the system moves farther north. Light winds will generally prevail across the local area, contributing to weak steering flow and potentially slow moving showers.

A warm and humid air mass will remain in place on Wednesday, with elevated moisture supporting widespread shower development, particularly across the interior and western portions of the island. Combined with daytime heating, sea breeze convergence, and orographic lifting, periods of heavy rainfall are possible. Light winds will result in weak steering flow, allowing showers to move slowly and increasing rainfall accumulations, with localized urban and small stream flooding possible. Wednesday is currently expected to be one of the wettest days of the period.

Somewhat drier air is forecast to filter into the mid and upper levels on Thursday and Friday, resulting in a slight decrease in available moisture and shower activity. Nevertheless, light winds, daytime heating, and local effects will continue to support afternoon showers, particularly across interior and western Puerto Rico. The overall flooding threat should decrease slightly during these days, although isolated heavy rainfall cannot be ruled out. Moisture is expected to increase again on Saturday as southerly to southwesterly winds transport additional tropical moisture into the region pulled by the low and frontal boundary moving across the Atlantic, north of Puerto Rico and USVI. This could make Saturday another one of the wettest days of the long term period, favoring shower and thunderstorm development. Light winds will still contribute to weak steering flow and potentially slow moving showers. Consequently, locally heavy rainfall could lead to increased accumulations and localized flooding.

By Sunday, drier air is expected to reach the region, favoring a decrease in available moisture and overall shower activity. Although isolated to scattered afternoon showers may still develop across the interior and western sections due to daytime heating and local effects, rainfall coverage and intensity should generally decrease. Continue to monitor the forecast as confidence increases and updated model guidance becomes available.

AVIATION

(18Z TAFS) Issued at 138 PM AST Sun Nov 1 2026

Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. However, tempo MVFR conds are possible at TJBQ thru 01/22z. Elsewhere, mostly VCSH expected due to locally induced -SHRA and passing trade wind showers. Winds will continue from the E up to 15 kt with sea breeze variations and stronger gusts until 01/21z, bcmg light and variable overnight.

MARINE

Issued at 138 PM AST Sun Nov 1 2026

The interaction between a surface high over the Western Atlantic and a low pressure over the Central Caribbean will increase the local pressure gradient and steering wind flow, with moderate easterly winds and building seas between 3 and 5 feet, occasionally 6 feet, across the regional waters and passages through Monday and Tuesday. Wednesday onwards, a low pressure area is forecast to develop over the Western Atlantic, weakening the local pressure gradient and winds, leading to light to moderate south-southwesterly winds. Passing showers and isolated thunderstorms will continue across the regional waters over the next few days, with locally higher winds and seas near thunderstorms; small craft should exercise caution.

BEACH FORECAST

Issued at 138 PM AST Sun Nov 1 2026

The moderate risk of rip currents continues across the northern and eastern-exposed beaches of Puerto Rico, including Culebra, and the U.S. Virgin Islands, low elsewhere. Although the risk is moderate, beachgoers must exercise caution as life-threatening rip currents are possible along the surf zone. As winds continue to strengthen, the moderate risk may expand into northwestern beaches of Puerto Rico and Vieques tomorrow, Monday. As winds gradually weaken later in the week, the risk should lower across most beaches of the islands. Nevertheless, beachgoers should always pay attention to the beach conditions as life-threatening rip currents can often occur near jetties, groins, piers, and reefs. In addition to rip currents, beachgoers should also remain weather alert, as showers and thunderstorms can be expected each day, pariculalry near coastal areas of western/northwestern Puerto Rico, without ruling out the San Juan Metro Area and the U.S. Virgin Islands. Periods of heavy showers, gusty winds, and heavy rainfall can be expected, beachgoers must must seek for shelter whenever they hear thunder.

SJU WATCHES/WARNINGS/ADVISORIES

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