textproduct: San Juan

KEY MESSAGES

Issued at 1244 PM AST Fri Aug 7 2026

- Warm to hot conditions will continue this weekend and early next week across the islands, particularly over urban and low- lying areas. The Heat Advisory remains in effect through 5:00 PM AST.

- Moderate concentrations of Saharan Dust will reach the local area tomorrow, with very high concentrations on Sunday and Monday. Sensitive groups must follow medical recommendations.

- A drier and more stable weather pattern will persist through the weekend. Limited rainfall is expected, allowing drought conditions to continue worsening across Puerto Rico and the U.S. Virgin Islands.

- Elevated fire weather conditions may persist for the next few days across southern and southwestern Puerto Rico due to critically dry fuels, low relative humidity, and breezy conditions.

Short Term(This evening through Sunday)

Issued at 1244 PM AST Fri Aug 7 2026

Sufficient lower-level moisture, combined with strong daytime heating and sea breeze convergence, will trigger diurnally induced afternoon showers across portions of the islands today. The heaviest showers with isolated thunderstorms will focus across the interior and western Puerto Rico, where ponding of water on roads or minor flooding is possible. In contrast, the U.S. Virgin Islands and eastern Puerto Rico will stay mostly sunny to partly cloudy with only brief, isolated showers. Maximum temperatures should reach the lower 90s across most coastal areas. The wind will prevail from the east to northeast around 15 mph.

A drying trend is expected into Saturday as a dense layer of Saharan dust moves over the northeastern Caribbean. Satellite observations and aerosol tracking indicate that the peak in density of the event will be from late Saturday into Sunday, causing a drop in moisture content to near or below 1 inch by early Saturday morning. This dense, dry air mass will create strong sinking air that prevents clouds and shower activity from building up. As a result, fair but particularly hazy skies will dominate the entire region through the end of the weekend, with rainfall remaining minimal across Puerto Rico and the U.S. Virgin Islands. However, a weak tropical wave is forecast to track just south of the area on Sunday, and guidance suggests a bump in precipitable water to near normal levels. Regardless, this should favor shower development again, mainly over western PR in the afternoon hours. At the same time, the rest of the area could see a slight increase in passing morning/evening showers.

With limited cloud cover and plenty of sunshine, temperatures will climb rapidly each afternoon, and due to the expected hazy conditions, warmer than normal minimum temperatures are possible. Therefore, warm to hot conditions are expected to prevail during the weekend. In addition, the dust event will reduce air quality, making outdoor activities hazardous for sensitive groups with respiratory conditions.

Long Term(Monday through next Thursday)

Issued at 1244 PM AST Fri Aug 7 2026

For the long-term period, a warm pattern is forecast through the first part of the period. The 12Z NASA GEOS-5 aerosol optical depth (AOD) guidance indicates a dense Saharan Air Layer (SAL) plume dominating the northeastern Caribbean early in the period. This high concentration of Saharan dust will promote strong radiative heating and warmer overnight temperatures. As a result, above-normal minimum and maximum temperatures will persist, particularly across coastal and urban areas. Meanwhile, an upper-level high pressure centered near 250 mb and extending across the eastern Caribbean will promote cirrus advection and periods of high-level cloudiness across the area on Monday. Therefore, residents are urged to stay tuned for possible heat-related alerts. Conditions will remain fairly similar through Tuesday morning, with warm temperatures continuing across the area but with lower concentrations of Saharan dust. A rapid change in the weather pattern is expected by Tuesday afternoon as surface high pressure strengthens north of the region. The resulting tight pressure gradient will induce a strong low-level easterly wind surge, promoting breezy to windy conditions across the local islands and surrounding waters.

Another pattern transition is expected by midweek as the axis of an easterly tropical wave approaches the local area on Wednesday, increasing column moisture and pushing precipitable water (PWAT) values toward 2.0 inches. According to the latest global model guidance, the peak in moisture is expected between Wednesday afternoon and Thursday morning. Depending on the extent of cloud cover and early-day convective activity, sufficient insolation combined with the moist boundary layer could make Wednesday the warmest day of the period. Nevertheless, local diurnal heating and sea-breeze convergence will promote afternoon convection, particularly across interior and western Puerto Rico. The tropical wave will maintain elevated low-level moisture into Thursday; however, forecast confidence regarding rainfall intensity and coverage remains low, as a drier air mass behind the wave axis could quickly move into the region and limit organized convection. By Friday, a more typical trade-wind pattern is expected to return, with lingering low-level moisture supporting brief passing showers across windward areas. Overall, above-normal temperatures and periods of elevated to significant heat risk are expected to persist through much of the extended period.

AVIATION

(18Z TAFS) Issued at 1244 PM AST Fri Aug 7 2026

Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. However, locally induced SHRA may cause brief MVFR cigs at TJPS thru 07/22z. Elsewhere, mostly VCSH expected. The 07/12z TJSJ sounding indicated ENE winds up to 20 kt blo FL080.

MARINE

Issued at 1244 PM AST Fri Aug 7 2026

A broad surface high building over the western Atlantic will maintain moderate east-to-northeasterly winds for the rest of the afternoon, becoming moderate to locally fresh, as winds continue to strengthen tonight. Building seas up to 6 feet may lead to choppy conditions across the regional waters and local passages. Afternoon thunderstorms near western coastal waters of Puerto Rico may produce gusty winds and locally hazardous conditions for small craft. A dense layer of Saharan Dust will gradually filter into the region on Saturday, with hazy skies, reduced visibility, and poor air quality through at least Tuesday.

BEACH FORECAST

Issued at 1244 PM AST Fri Aug 7 2026

No changes were introduced to the beach forecast. The moderate risk of rip currents continues across northern and eastern beaches of Puerto Rico, including Vieques and Culebra, and the U.S. Virgin Islands; low elsewhere. Although the risk is moderate, beachgoers must exercise caution as life-threatening rip currents remain possible along the surf zone. As winds continue to gradually strengthen this weekend, the moderate risk may spread across most beaches of Puerto Rico and the U.S. Virgin Islands. Besides rip currents, beachgoers visiting beaches in the western side of Puerto Rico should remain alert as isolated thunderstorms could move near the coastal areas and produce gusty winds and lightning. Moderate to very high concentrations of Saharan Dust will move across the region this weekend and early next week, bringing hazy skies and reduced visibility.

FIRE WEATHER

Issued at 1244 PM AST Fri Aug 7 2026

Critical fuel conditions persist across the islands, with extreme drought conditions across portions of the southern coastal plains of Puerto Rico. RAWS stations have reported winds between 8 - 13 mph and gusts up to 25 mph during the morning hours. Additionally, as a drier air mass continues to filter into the region, moisture content has dropped significantly, with RH values between 47 and 54 %, well below thresholds. Due to critical fuel conditions across the southern area of the island and KDBI values well above thresholds, the fire danger threat remains elevated. Hence, the Fire Danger Statement continues in effect through 5 PM AST. Residents and visitors are encouraged to avoid outdoor burning, as conditions will likely be favorable for wildfire ignition and rapid spread.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007- 008-010>013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...None.