textproduct: San Juan

KEY MESSAGES

Issued at 310 AM AST Sat Aug 22 2026

* Hot and humid conditions will maintain an elevated heat threat across coastal and urban areas, with heat indices potentially reaching around 110F. A Heat Advisory is in effect for areas where the highest heat indices are expected from 10 AM to 5 PM AST today.

* Variable weather conditions are expected today, with periods of passing showers alternating, followed by additional afternoon shower development due to daytime heating and local effects.

* A weak tropical wave will approach and move across the region on Monday, increasing moisture and the frequency of showers, although the deepest moisture is expected to remain mainly south over the Caribbean waters.

* A low to moderate risk of rip currents will continue across several local beaches for the upcoming days.

Short Term(Today through Monday)

Issued at 310 AM AST Sat Aug 22 2026

Isolated to scattered showers were observed from late Friday into the early morning hours on Saturday across most of the region. A line of showers moved across the area from east to west, resulting in variable weather conditions with generally minimal rainfall accumulations. The strongest showers were detected by Doppler radar just south of the coastal areas between Ponce and Juana Diaz. Shower activity also moved westward, affecting several northern coastal municipalities before gradually diminishing around 2 AM. Overnight temperatures were in the lower 80s across coastal areas and in the lower to mid-70s across the mountainous sections. Winds were generally from the east-northeast at around 10 mph, with occasional gusts accompanying the showers.

East-northeasterly winds will remain in place through at least the early morning hours today, gradually becoming more easterly and allowing showers to affect eastern and northeastern Puerto Rico. Sufficient moisture will continue to reach the islands as a patch of moisture moves across the region, followed by another area of moisture during the afternoon, with precipitable water values ranging from 1.8 to 1.9 inches. These conditions will support a showery pattern under breezy conditions, as a surface high pressure system over the western Atlantic maintains a tight pressure gradient across the region. Given the expected conditions, showers will generally be fast-moving, keeping rainfall accumulations on the lower side, particularly across eastern Puerto Rico and the eastern interior. By the afternoon, high-resolution models suggest an increase in shower activity across northwestern and western interior Puerto Rico, mainly due to diurnal heating and local effects. These factors could support locally moderate to briefly heavy showers; however, the presence of a mid-level ridge will inhibit more widespread and persistent shower development.

On Sunday, at the surface, a high-pressure system over the Atlantic, in combination with an area of low pressure over the central Atlantic, will promote a more east-southeasterly wind flow across the region. According to the global model guidance, during the morning hours, a relatively dry slot of air is expected to filter into the local area, limiting the frequency and coverage of shower activity. Therefore, generally fair weather conditions should prevail for much of the morning, although a few brief showers cannot be ruled out, especially across windward coastal areas. Moisture is then expected to gradually increase from the late morning into the afternoon, with precipitable water values increasing. The combination of this increase in available moisture, daytime heating, and local effects should support afternoon shower development, mainly across portions of the interior and western to northwestern Puerto Rico. Given the expected steering flow, showers should generally move toward the west-northwest. However, the overall environment is not expected to be particularly unstable, which should limit the potential for widespread or prolonged rainfall activity. By Monday, the low- level wind flow is expected to become more easterly as a weak tropical wave approaches and moves across the region. Moisture will increase in association with the wave, resulting in a slightly wetter pattern compared to Sunday. Although the bulk of the tropical moisture is forecast to pass south of the islands and remain primarily over the Caribbean waters, the northern portion of the moisture field should extend across Puerto Rico and the U.S. Virgin Islands. This should be sufficient to increase the frequency of passing showers across eastern Puerto Rico and the local waters during the morning hours.

In addition to the rainfall potential, heat will remain a concern through Sunday and Monday, particularly across the coastal and urban areas of Puerto Rico and the U.S. Virgin Islands. Warm temperatures combined with elevated low-level moisture will result in heat indices potentially reaching around 110F across some coastal and urban locations. The highest heat indices are expected during the late morning and early afternoon hours, before afternoon shower activity provides some localized relief. Therefore, residents should remain aware of the potential for heat-related impacts, especially in areas where shower activity remains limited.

AVIATION

(06Z TAFS) Issued at 310 AM AST Sat Aug 22 2026

VFR conds are expected to prevail across all local terminals through the fcst period. E-ENE winds at 10-15 kt will prevail, increasing to 15 kt aft 22/14Z. Passing SHRA will continue to move across the local area, mainly affecting TJSJ/TIST/TISX during the AM hrs. Brief -SHRA/SHRA may result in tempo reduced VIS and lower CIGs at times. Aft 22/16Z, diurnal heating and local effects will favor SHRA development across interior and W/NW PR.

MARINE

Issued at 310 AM AST Sat Aug 22 2026

A surface high pressure over the Western Atlantic in combination with a low pressure system across the central Atlantic will allow moderate easterly winds across the region. This will favor seas between 3-5 feet with occasionally seas up o 6 feet across offshore Atlantic waters. Given the expected conditions, mariners should stay tune for weather updates. Today some showers with thunderstorms can result in localized hazardous marine conditions.

BEACH FORECAST

Issued at 310 AM AST Sat Aug 22 2026

Expect risk to be low across most islands through at least Monday. Regardless, life-threatening rip currents can occur near groins, jetties, reefs, and piers. From Tuesday into midweek, winds are expected to gradually become breezier, with a moderate risk expanding to most local beaches.

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.