textproduct: San Juan

KEY MESSAGES

Issued at 246 AM AST Thu Aug 6 2026

- Hot and hazardous conditions will remain the primary weather concern through the remainder of the week and into the weekend. Heat Advisory in effect through 5 PM AST this afternoon across Puerto Rico and the U.S. Virgin Islands, and additional heat products will likely be needed in the coming days as above- normal temperatures and dangerous heat indices persist.

- Passing showers will continue this afternoon, mainly across the interior and western to northwestern sections of Puerto Rico.

- Limited fire weather conditions today. Lower relative humidity, drying fuels, and breezy east to east- southeast winds could maintain the potential for rapid wildfire spread, particularly across areas with dry vegetation. Residents should avoid outdoor burning and exercise caution with activities that could produce sparks.

Short Term(Today through Saturday)

Issued at 246 AM AST Thu Aug 6 2026

Overnight conditions remained tranquil across the local islands. Light and variable winds combined with mostly clear skies favored efficient radiational cooling, allowing temperatures to fall into the mid-70s across the coastal and urban areas, while the mountains cooled into the upper 60s to lower 70s.

A surface high over the western Atlantic will gradually strengthen through the short-term period, maintaining an east-southeasterly wind flow today before shifting to the east-northeast on Friday. At the same time, a drier air mass will continue filtering across the region, with precipitable water values falling to around 1.2 to 1.4 inches and mid-level relative humidity dropping below 30 to 40 percent. This combination will promote a more stable pattern through Saturday, limiting convection to the typical diurnal cycle. Expect a few passing showers across the windward sectors during the overnight and morning hours, followed by isolated afternoon showers over the interior and western sections of Puerto Rico, where daytime heating and local effects will provide sufficient lift. With a stronger steering flow, showers should remain frequent, keeping rainfall accumulations localized and the flood threat limited.

The primary weather concern through Saturday will be the heat. The east-southeasterly flow today will continue to favor the warmest temperatures across the northern, western, and urban sections of Puerto Rico before a more easterly to east-northeasterly wind develops on Friday. Afternoon highs will generally reach the upper 80s to low 90s across the coastal and urban areas of Puerto Rico, while the higher elevations remain in the lower 80s. Across the U.S. Virgin Islands, highs will range from the upper 80s to around 90 degrees. Despite the drier air aloft, enough low-level moisture will persist to produce hazardous heat index values across coastal and urban areas. Therefore, a Heat Advisory remains in effect today, and additional heat products may be needed through Friday if these conditions continue.

Long Term(Sunday through Thursday)

Issued at 246 AM AST Thu Aug 6 2026

A progressive weather pattern is expected as tropical waves, easterly wind surges, and a TUTT low move through or near the eastern Caribbean. The first wave will approach Sunday and move across the region through Monday. Although the deepest moisture should remain mainly over the Caribbean waters, Sunday and Monday currently appear to have the greatest potential for increased shower and thunderstorm coverage. Afternoon convection should be most noticeable over interior and western Puerto Rico, with an elevated lightning risk where thunderstorms develop.

A brief period of lower moisture is possible late Monday into early Tuesday, followed by a strong easterly wind surge. Breezy to windy conditions will prevail through much of the period, with Tuesday potentially becoming the windiest day. Moisture may increase again from Wednesday into Thursday as another tropical wave approaches, but confidence in its timing and associated rainfall remains low. Wednesday could become the warmest day if cloud and shower coverage remains limited, with elevated to significant heat risks continuing through the period.

Despite occasional increases in moisture and convection, widespread or prolonged rainfall is not anticipated. Therefore, significant relief from the ongoing severe drought and water-supply concerns is unlikely. Rainfall and lightning impacts will depend greatly on the timing of each feature and how much tropical moisture reaches the local islands.

AVIATION

(06Z TAFS) Issued at 246 AM AST Thu Aug 6 2026

VFR conditions across all TAF sites. VCSH will develop over west PR and TJBQ from 06/17Z trough 06/23Z. Winds will remain from the E around 10 to 15 kts and occasional higher gusts.

MARINE

Issued at 246 AM AST Thu Aug 6 2026

A broad surface high pressure over the central Atlantic will maintain a moderate easterly wind flow across the regional waters through today, with generally favorable marine conditions prevailing. Seas will remain between 3 and 5 feet, occasionally up to 6 feet across the offshore Atlantic waters and local passages by late tonight as the pressure gradient gradually tightens. East to east-southeasterly winds will increase to 15 to 20 knots through the end of the week and into the weekend, leading to choppier seas, especially across the Atlantic waters, Anegada Passage, and Caribbean passages. Isolated afternoon thunderstorms developing over western Puerto Rico may briefly produce locally higher winds, rough seas, and frequent lightning. In addition, moderate concentrations of Saharan dust are expected to return late Friday and persist through the weekend, occasionally reducing visibility across the local waters. Overall, small craft operators should continue to monitor the latest forecasts as marine conditions could deteriorate.

BEACH FORECAST

Issued at 246 AM AST Thu Aug 6 2026

A moderate risk of rip currents is expected across all northern coastal areas of Puerto Rico due to a slight increase in surface winds across the local waters. For the rest of the area, including the U.S. Virgin Islands, the risk will remain low. For tonight, the risk will increase for Culebra and St. Croix. In terms of beach hazard, heat remains the primary beach hazard through the remainder of the week. Some shower activity across western sections would result in a lightning threat across western sections.

FIRE WEATHER

Issued at 246 AM AST Thu Aug 6 2026

Critically dry fuels continue across portions of the local islands, particularly across southern Puerto Rico, St. Croix, and other fire- prone areas of the U.S. Virgin Islands. Although isolated showers and localized thunderstorms remain possible this afternoon, mainly across interior and western Puerto Rico, recent rainfall has been limited over the southern coastal plains, where fuels remain receptive to fire starts. Winds will remain relatively light today, keeping the fire weather threat limited through the remainder of the afternoon.

A drier and more stable weather pattern will become established beginning today and persist into the weekend as moisture decreases and easterly winds strengthen. Lower relative humidity, increasing sunshine, and breezy conditions, combined with critically dry fuels, will elevate the potential for rapid wildfire growth and spread, particularly across southern Puerto Rico and the U.S. Virgin Islands. Residents and visitors are encouraged to avoid outdoor burning and use caution with activities that could produce sparks, as fire weather conditions are expected to become increasingly favorable in the coming days.

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.