textproduct: San Juan

KEY MESSAGES

Updated at 303 AM AST Wed Aug 26 2026

* Dangerous Heat Continues: Extreme heat conditions are expected today in PR and the USVI, with elevated to locally significant heat risks continuing through the remainder of the week.

* Saharan Dust Today: Moderate Saharan dust concentrations will maintain hazy skies and may reduce air quality before gradually decreasing tonight into Thursday.

* Limited Flooding Risk: Afternoon showers and isolated thunderstorms may produce locally heavy rainfall, mainly across interior and southwestern Puerto Rico, but widespread flooding is not expected.

* Brief Tropical Wave: A weak tropical wave will move quickly across the region late Friday night into Saturday morning, temporarily increasing showers and thunderstorms before significantly drier conditions return Sunday.

* Increasing Rip Current Risk: The potential for life- threatening rip currents will increase to moderate from this evening onward, especially along most exposed beaches of Puerto Rico and the US Virgin Islands.

Short Term(Today through Friday)

Issued at 303 AM AST Wed Aug 26 2026

Hazy skies prevailed overnight as moderate concentrations of Saharan dust remained across the region. Limited radiational cooling contributed to another warmer-than-normal night, with temperatures generally in the upper 70s to low 80s across coastal areas, locally reaching the mid-80s, and considerably cooler temperatures across higher elevations and sheltered valleys. Doppler radar detected only a few showers, mainly over the local waters, while light to calm winds prevailed under land-breeze influences.

Temperatures will start warmer than normal today and, combined with available low-level moisture, will result in dangerously high heat indices. An Extreme Heat Warning is in effect for urban and coastal portions of Puerto Rico, while a Heat Advisory is in effect for Culebra, Vieques, St. Thomas, St. John, and St. Croix from 9 AM to 5 PM AST. Moderate Saharan dust concentrations will also keep skies hazy and air quality potentially reduced through this evening.

Despite the relatively drier air mass, available low-level moisture combined with strong daytime heating, sea-breeze convergence, and local effects will support isolated to scattered afternoon showers and thunderstorms, mainly across the interior and southwestern quadrant of Puerto Rico. Locally heavy rainfall could result in a limited flooding risk. Another moisture surge will arrive late tonight into Thursday, gradually reducing Saharan dust concentrations and increasing passing showers across the local waters and windward portions of Puerto Rico and the USVI. Elevated to locally significant heat risks will persist Thursday, particularly across urban and coastal areas. Afternoon convection will again favor interior and western Puerto Rico. Widespread flooding is not anticipated, but a limited flooding risk will persist where locally heavy rainfall develops.

Model guidance suggests increasing subsidence on Friday ahead of another weak tropical wave, limiting shower activity through at least Friday evening while allowing the hot spell to persist across the islands. The wave and its associated moisture are then expected to approach late Friday night into early Saturday, marking the transition toward a brief wetter pattern discussed in the Long Term.

Long Term(Saturday through Wednesday)

Issued at 303 AM AST Wed Aug 26 2026

A brief, weak tropical wave will move quickly across the region between late Friday night and Saturday morning, temporarily increasing moisture and supporting passing showers and isolated thunderstorms across Puerto Rico and the U.S. Virgin Islands. A rapid drying trend is expected behind the wave, as a dominant surface high settles over the central Atlantic and a mid-level ridge builds across the region. Drier and more stable conditions should become established by Sunday, with precipitable water values falling below climatological normals to around 1.25 inches through Monday morning.

Uncertainty increases during the second half of the forecast period, as local conditions will depend on the track and future intensity of tropical wave AL96, currently south-southwest of the Cabo Verde Islands. Latest guidance still suggests the system will pass northeast of the region between Monday afternoon and Wednesday. Nevertheless, its evolution will continue to be monitored for potential indirect impacts. Given the uncertainty, residents and local interests should monitor subsequent forecasts as AL96 moves across the Atlantic.

Meanwhile, seasonal to above-seasonal 925-mb temperatures will persist throughout the period, resulting in elevated to possibly significant heat risks each day.

AVIATION

(06Z TAFS) Issued at 303 AM AST Wed Aug 26 2026

Mainly VFR conds expected across all terminals. Saharan dust will maintain HZ today, with VIS generally remaining VFR. SHRA/isol TSRA may develop across interior and SW PR this afternoon, potentially affecting the VCTY of TJPS with brief MVFR and mount obsc. Increasing moisture tonight into Thu will favor additional SHRA across windward PR/USVI. E-ENE winds at 10-15 kt with sea breeze variations aft 26/13z, becoming lighter overnight with land breeze and higher gusts near convection.

MARINE

Issued at 303 AM AST Wed Aug 26 2026

Surface high across the western and central Atlantic will continue to support moderate, locally fresh at times, east to east- northeasterly steering flow today before becoming more east to east-southeast tomorrow through the rest of the week. Patches of moisture will continue to steer showers over the region while afternoon convection can move off the coast of western PR each day. Saharan dust concentrations will peak today, resulting in hazy skies and slightly reduced visibility, and gradually decrease late tonight. A weak long-period northerly swell remains forecast to arrive and spread across the regional waters by tomorrow, Thursday. A broad moisture field from a tropical wave is forecast to stay mainly over the southern waters Friday to Saturday.

BEACH FORECAST

Issued at 303 AM AST Wed Aug 26 2026

A low risk of rip currents will continue until at least this evening across the local islands. However, life-threatening rip currents often occur in the vicinity of groins, jetties, reefs, and piers.

A gradual increase in winds and seas will then result in a moderate risk of rip currents (life-threatening rip currents are possible in the surf zone) this evening onwards, particularly along the northern and eastern-exposed beaches of the islands through the end of the week.

A broad moisture field from a tropical wave is forecast to stay mainly south of the islands Friday and Saturday but can result in showers and isolated t-storms across coastal areas. Afternoon convection each day can also affect mainly western coastal areas (W- SW today and W-NW tomorrow through the end of the week). Beachgoers should remain weather alert, as thunderstorms could produce gusty winds and dangerous lightning.

FIRE WEATHER

Issued at 303 AM AST Wed Aug 26 2026

A marginal fire weather risk is expected today, primarily due to dry fuels. Relative humidity values may briefly decrease during peak heating; however, available low-level moisture should keep conditions above critical thresholds. Winds will remain below normal, limiting the potential for rapid fire spread. Overall, dry fuels remain the primary concern, while lighter winds and sufficient humidity should limit the fire weather threat.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Extreme Heat Warning from 9 AM this morning to 5 PM AST this afternoon for PRZ001>005-007-008-010-011.

Heat Advisory from 9 AM this morning to 5 PM AST this afternoon for PRZ012-013.

VI...Heat Advisory from 9 AM this morning to 5 PM AST this afternoon for VIZ001-002.

AM...None.