textproduct: San Juan

KEY MESSAGES

Issued at 345 AM AST Thu Nov 12 2026

- The main hazard over the coming days will be the heat. Hot, humid conditions will pose the highest risks across coastal areas, lowlands, interior valleys, and urban zones. A Heat Advisory is in effect today from 10 AM to 5 PM AST.

- Generally fair weather will prevail over the coming days, however, a few showers are expected across the USVI and PR's windward areas in the mornings, with localized afternoon shower development across southeast and northwest PR.

- Southeast winds will gradually increase, becoming breezy, especially Friday and Saturday.

- Life-threatening rip currents will remain possible (moderate risk) across most local beaches of PR and USVI throughout the forecast period.

Short Term(Today through Saturday)

Issued at 345 AM AST Thu Nov 12 2026

Satellite and radar imagery showed mainly clear skies and fair weather conditions during the overnight period. Surface observations registered temperatures in the mid to upper 70s across coastal areas and in the 60s to low 70s across mountainous regions. Winds remained light and variable.

A mid to upper-level ridge near the region will maintain subsidence and dry air aloft, favoring generally fair weather across most of Puerto Rico and the U.S. Virgin Islands throughout the forecast period. At the surface, seasonal precipitable water values will prevail. The main weather hazard today, and likely over the coming days, will be the heat due to the combination of southeast winds and low-level moisture. A Heat Advisory is in effect from 10 AM to 5 PM AST for Puerto Rico and the U.S. Virgin Islands. Hot and humid conditions will pose the greatest risks across coastal areas, lowlands, interior valleys, and urban areas.

Today, a shortwave trough passing north of the islands will slightly weaken the ridge pattern aloft, allowing for a slight increase in moisture levels between 850 and 500 mb. Consequently, the frequency of passing showers will increase across eastern to southern portions of Puerto Rico and the U.S. Virgin Islands, particularly during the afternoon and evening. Daytime heating and local effects may trigger isolated to scattered showers across portions of northwestern Puerto Rico. However, overall atmospheric stability will dominate and should keep rainfall activity localized.

On Friday and Saturday, a surface high pressure over the central Atlantic, along with the mid to upper-level ridge prevailing across our area, will result in persistent subsidence and limited shower coverage. The main weather concerns will remain the heat and southeast winds, which are expected to become breezier on those days as the pressure gradient tightens across the eastern Caribbean.

Long Term(Sunday through Thursday)

Issued at 345 AM AST Thu Nov 12 2026

No major changes were introduced to the long-term forecast. The interaction with a surface high pressure over the Central Atlantic and a frontal boundary north of the CWA should slightly weaken local pressure gradient, maintaining a E-SE wind flow. Aloft, a mid-level ridge in the vicinity should dominate most of the weather pattern, as model guidance suggest slightly warmer than normal mid-level temperatures throughout most of the forecast period. Sunday should be the less active day of the long-term, as model guidance suggest well below normal moisture content in the low and mid levels. Shower activity (if any) during the afternoon should remain isolated and short-lived. On Monday, model guidance suggest the arrival of a patch of moisture in the early morning, increasing frequency of showers over windward areas. From the latest model solutions, it seems that PWATs may push back into normal values, however, it mainly concentrates in the 1000-850 and 300 - 200 mb layers, while the mid-levels remain dry. Additionally, the latest NASA AOT suggest low concentrations of SAL lingering in the CWA. Although these conditions will limit deep convection, daytime heating and local effects will trigger afternoon convection across interior and western/northwestern Puerto Rico. Rainfall accumulations could increase the likelihood of ponding of water over roadways and poorly drained areas, though the urban and small stream flood should remain isolated. A similar weather pattern can be expected on Tuesday and Wednesday, though the flood threat should remain low.

AVIATION

(06Z TAFS) Issued at 345 AM AST Thu Nov 12 2026

Mainly VFR conditions are expected to prevail across all TAF sites during the forecast period. However, locally induced VCSH/-SHRA may develop in and around TJBQ/TISX/TIST/TJPS between 12/17-22Z. This can result in intermittent/brief MVFR conds. SE winds up to 12 kt with sea breeze variations and gusts up to 18 to 20 kt (in TJSJ and TJPS) expected aft 12/13-14z.

MARINE

Issued at 345 AM AST Thu Nov 12 2026

Surface high pressure over the central Atlantic will strengthen east- to-southeast trade winds through Saturday, with winds increasing to 15 to 20 knots and gusts up to 30 knots, particularly Friday. Although the northerly swell will continue to subside, increasing wind-driven seas will produce choppy to locally rough conditions, with seas generally between 3 and 6 feet, occasionally reaching 8 feet across portions of the offshore waters and local passages. Small craft should exercise caution, with the most hazardous conditions expected Friday. Showers and isolated thunderstorms may produce locally higher winds and seas. Marine conditions should gradually improve Sunday into early next week.

BEACH FORECAST

Issued at 345 AM AST Thu Nov 12 2026

A moderate risk of life-threatening rip currents will persist through Saturday along most northern and eastern beaches of Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands, extending into portions of the southern and western beaches. Beginning Sunday, some improvement is expected as the risk gradually decreases to low along more of the southern and western beaches of Puerto Rico and portions of the smaller islands. However, a moderate risk will continue along exposed northern and eastern beaches through early next week. Beachgoers should remain cautious, as life-threatening rip currents are possible in the surf zone. Lightning may pose an additional hazard where afternoon thunderstorms develop.

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.