textproduct: San Juan

KEY MESSAGES

Issued at 145 AM AST Tue Aug 11 2026

- Showers and isolated thunderstorms will increase today, with the greatest localized flooding risk expected during this period. Lightning and gusty winds will also be possible.

- Heat risks will remain elevated through the week, although increased clouds and showers may limit daytime heating today. Significant heat risk becomes more likely Wednesday as drier conditions and greater sunshine return, with another increase possible this weekend. Warm overnight temperatures will continue to provide limited relief.

- Stronger trade winds will develop late this week and continue into the weekend, increasing wind and marine hazards, building seas, and resulting in a high risk of rip currents beginning Thursday.

- NHC continues to monitor multiple Atlantic disturbances. It remains too early to determine any potential impacts to Puerto Rico or the U.S. Virgin Islands.

Short Term(Today through Thursday)

Issued at 145 AM AST Tue Aug 11 2026

A tropical wave will move across the northeastern Caribbean today into early Wednesday, with its axis crossing the Lesser Antilles this morning and the local area tonight before reaching Hispaniola Wednesday morning. A broad surge of tropical moisture ahead of and along the wave will increase precipitable water to around 2 inches today, while an upper-level trough near the eastern Greater Antilles provides some additional support for convection. Drier Saharan air will gradually spread into the region behind the wave Wednesday, becoming more established Wednesday night into Thursday. At the same time, the Atlantic ridge will shift southward and strengthen the local pressure gradient, resulting in increasing easterly trade winds Wednesday night through Thursday. Another tropical wave will approach the Lesser Antilles late Thursday, but its main influence should remain east of the local area through the end of the period.

The greatest rainfall and thunderstorm potential will occur today as tropical moisture combines with daytime heating, sea-breeze convergence, and local terrain effects. Showers will increase across the U.S. Virgin Islands and eastern Puerto Rico, followed by scattered afternoon convection across interior and western Puerto Rico. Although weak mid-level lapse rates should limit widespread deep convection, sufficient moisture and instability will support isolated thunderstorms capable of lightning, gusty winds, and locally heavy rainfall, with localized urban and small- stream flooding possible. Increased cloud cover and shower activity may limit daytime heating today, although localized elevated heat risk will remain possible where longer periods of sunshine occur. Residual moisture may support additional showers early Wednesday before drying increases and convective coverage decreases. Greater sunshine and warm low-level temperatures should then allow heat risk to increase, with significant heat impacts possible Wednesday across the typically warmer urban and coastal areas. Warm overnight temperatures will continue to provide limited relief. By Thursday, below-normal moisture, Saharan dust, and increasing trade winds should limit rainfall mainly to brief windward showers while promoting hazy and breezy conditions.

Long Term(Friday through Tuesday)

Issued at 145 AM AST Tue Aug 11 2026

A tightening pressure gradient associated with the Atlantic high is expected to support breezy to locally windy east to northeast winds through much of the long-term period. Gusty conditions could affect unsecured outdoor items, particularly across exposed coastal and higher-elevation areas. Winds could approach advisory criteria at times, although confidence in the magnitude and duration of the strongest winds remains limited. Saharan dust and a relatively dry air mass should otherwise dominate much of the period, with precipitable water values generally remaining below normal near 1.3 inches. Intermittent patches of low-level moisture may support passing windward showers and highly localized afternoon convection. Elevated heat risk will also persist, with locally significant heat impacts possible across the warmer urban and coastal areas. Warm overnight temperatures will continue to provide limited relief.

Forecast uncertainty increases considerably late in the period as the National Hurricane Center continues to monitor a tropical disturbance over the central Atlantic. While development is possible as the system moves generally westward, considerable uncertainty remains regarding its eventual track, intensity, timing, and whether it could have any direct or indirect influence on Puerto Rico and the U.S. Virgin Islands early next week. Continue to monitor subsequent forecasts and Tropical Weather Outlooks from the National Hurricane Center as the forecast evolves.

AVIATION

(06Z TAFS) Issued at 145 AM AST Tue Aug 11 2026

Increasing moisture ahead of an approaching TW will support frequent SHRA across the terminals through the day. ISOLD TSRA are possible near TJSJ, with greater TSRA coverage expected in and around TJBQ during the aftn. Brief MVFR or lower CIG/VSBY are possible with heavier SHRA/TSRA. HZ may also reduce VSBY to around 6SM at times. SFC winds 10-15 kt, increasing to 15-20 kt after 11/13Z, with higher gusts and VRB winds near convection.

MARINE

Issued at 145 AM AST Tue Aug 11 2026

The broad Atlantic ridge extending from the western into the central Atlantic will continue to promote moderate easterly winds across the local waters today. A tropical wave crossing the eastern Caribbean will increase shower and thunderstorm activity, with locally higher winds and seas possible near stronger convection. Marine conditions will deteriorate toward the end of the workweek as the local pressure gradient tightens and easterly winds strengthen. Fresh to locally strong winds and increasingly rough seas are expected across portions of the offshore waters and local passages, resulting in hazardous conditions for small craft. Small Craft Advisories will likely be required for some of these waters. Pulses of Saharan dust will also persist through the week, occasionally reducing visibility.

BEACH FORECAST

Issued at 145 AM AST Tue Aug 11 2026

A moderate risk of rip currents continues along many of the northern and eastern beaches of Puerto Rico, including Vieques and Culebra, as well as portions of the U.S. Virgin Islands. A tropical wave crossing the region today will also increase the potential for showers and thunderstorms near coastal areas. Periods of heavy rainfall, gusty winds, and lightning will be possible, and beachgoers should seek shelter whenever thunder is heard.

Beach conditions are expected to become increasingly hazardous toward the end of the workweek as strengthening easterly winds generate larger breaking waves along exposed coastlines. The rip current risk will likely increase to high across many north- and east-facing beaches of Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands. Life-threatening rip currents will become more likely, and Rip Current Statements may be required as conditions deteriorate. Residents, visitors, and beachgoers should monitor subsequent forecasts and any statements issued over the next few days.

FIRE WEATHER

Issued at 145 AM AST Tue Aug 11 2026

A more humid environment today should generally limit the potential for critical fire weather conditions. However, very dry and stressed fuels, along with high KBDI values, remain a concern across Puerto Rico. Therefore, despite higher moisture levels, locally breezy conditions could still support fire growth and spread where ignitions occur. Outdoor burning is discouraged given the current state of the fuels.

SJU WATCHES/WARNINGS/ADVISORIES

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