textproduct: San Juan

KEY MESSAGES

Issued at 157 AM AST Sat Aug 8 2026

- Heat Advisory for Puerto Rico and the US Virgin Islands as we forecast hot conditions today. This warm weather pattern should prevail through the end of the weekend, particularly over urban and low lying areas.

- 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.

- Moderate concentrations of Saharan Dust will reach the local area today, 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.

Short Term(Today through Monday)

Issued at 157 AM AST Sat Aug 8 2026

Similar to previous nights, generally calm weather prevailed overnight, with mostly clear skies across Puerto Rico and the U.S. Virgin Islands. Winds were light and mainly easterly, while temperatures ranged from the upper 70s to lower 80s along the coast and remained in the 70s across the interior and higher areas. Light concentrations of Saharan dust gradually reached the U.S. Virgin Islands and eastern Puerto Rico overnight.

Today, dry, warm and stable conditions will accompany the arrival of a dense Saharan Air Layer. The latest model guidance suggest precipitable water values falling well below normal for this time of the year along with RH at mid- levels suppressing shower development. Therefore, mostly fair weather with increasingly hazy skies and limited rainfall is expected across Puerto Rico and the U.S. Virgin Islands. A Heat Advisory was issued for the coastal and urban areas of Puerto Rico and the US Virgin Islands, this will be in effect from 10 AM through 5 PM today.

The Saharan dust event is expected to peak on Sunday, with dust aerosol guidance indicating high concentrations across the region. A weak tropical wave mainly south of the islands will bring some moisture back into the area. However, the dry and stable air associated with the Saharan Air Layer should limit the development of any significant rainfall. By Monday, dust concentrations should gradually decrease as deeper tropical moisture returns, allowing a more typical pattern of passing windward showers and afternoon convection across western Puerto Rico.

Heat, haze, and poor air quality will be the main impacts through the weekend. Abundant sunshine will promote rapid daytime heating, while the dense dust layer may limit overnight cooling and allow each day to begin with already warm temperatures. As tropical moisture increases, the combination of heat and humidity will make conditions uncomfortable. Meanwhile, high dust concentrations, particularly on Sunday, will reduce air quality and could aggravate respiratory conditions. Residents and visitors, especially those sensitive to poor air quality and excessive heat, should limit prolonged outdoor exposure, stay hydrated, and take frequent breaks in shaded or air-conditioned areas.

Long Term(Tuesday through Saturday)

Issued at 157 AM AST Sat Aug 8 2026

Weather conditions during the long-term period will turn more variable with the arrival of a wind surge and a tropical wave across the CWA. On Tuesday, a surface high pressure anchored over the Central Atlantic will maintain easterly winds, pushing a weak wind surge in the 700 to 500 mb layer across the area. Precipitable water values are forecast by the GFS and ECMWF to range between 1.6 and 1.8 inches, which will be enough moisture to enhance afternoon convection along the western sections of the islands. From late Tuesday into Wednesday, surface winds will shift more from the southeast due to the interaction between the Atlantic surface high and the approaching tropical wave. The peak of this moisture field is forecast for Wednesday afternoon, favoring a variable weather pattern with morning to early afternoon showers along northeastern Puerto Rico, followed by deep afternoon convection along the western coast driven by local effects. Although rainfall accumulations of 1 to 2 inches are possible with the heaviest showers, this will not be enough to mitigate existing drought conditions across the island.

A rapid drying trend is forecast by Thursday as a drier air mass moves back into the region, limiting overall shower development across the area. By Friday, global model guidance suggests another tropical wave tracking across the Caribbean region. As of today, the GFS keeps the bulk of the moisture moving over the Caribbean waters south of the local area. However, given the extended time frame of the forecast, changes to the moisture track and intensity remain possible by the end of the period.

AVIATION

(06Z TAFS) Issued at 157 AM AST Sat Aug 8 2026

Mostly VFR conditions across all TAF sites. Moderate concentrations of HZ will prevail across all terminal from 08/12Z onwards. Brief periods of MVFR condt possible due to VCTS near TJBQ and TJPS from 08/17Z trough 08/23Z. Winds will remain from the E around 15 kts and occasional higher gusts.

MARINE

Issued at 157 AM AST Sat Aug 8 2026

A broad surface high over the Atlantic will maintain moderate to fresh easterly winds tonight, with winds strengthening through the weekend. Marine conditions will become increasingly choppy, with the highest risk for hazardous conditions Sunday into Monday, particularly across the offshore waters and local passages. Afternoon thunderstorms may produce locally hazardous winds and seas, while Saharan dust may reduce visibility through the weekend.

BEACH FORECAST

Issued at 157 AM AST Sat Aug 8 2026

A moderate risk of rip currents will continue along the north- and east- to southeast-facing beaches of Puerto Rico into early next week. The risk should decrease to low across most beaches by midweek, before increasing to moderate Thursday and potentially high Friday into next weekend as easterly winds strengthen significantly.

Heat will remain the primary beach hazard this weekend, while isolated afternoon thunderstorms over western Puerto Rico may produce dangerous cloud-to-water lightning. A dense Saharan dust plume will arrive Saturday morning, peaking Saturday evening into Sunday, with reduced visibility and hazy conditions expected.

FIRE WEATHER

Issued at 157 AM AST Sat Aug 8 2026

Critical fuel conditions persist across the islands, with extreme drought conditions across portions of the southern coastal plains of Puerto Rico. As a drier air mass continues to filter into the region, moisture content will drop significantly, with RH values between 47 and 50 percent, 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. Therefore, a Fire Danger Statement is in effect from 10 AM 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 from 10 AM this morning to 5 PM AST this afternoon for PRZ001>005-007-008-010>013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for VIZ001-002.

AM...None.