textproduct: San Juan

KEY MESSAGES

Issued at 355 AM AST Fri May 15 2026

* Hot and humid conditions will continue across Puerto Rico and the U.S. Virgin Islands through much of next week, with elevated heat indices likely in urban and coastal areas each day.

* Passing showers will continue across eastern Puerto Rico and the U.S. Virgin Islands during the overnight and morning hours, followed by afternoon convection across western Puerto Rico.

* A wetter weather pattern is expected to develop next week as moisture levels increase and an upper-level trough approaches the region. This may result in more frequent showers and isolated thunderstorms, especially across western and northwestern Puerto Rico and portions of the San Juan metro area.

* The main hazards throughout the period will continue to be localized flooding from heavy rainfall and excessive heat impacts from warm temperatures and high humidity.

* A moderate risk of rip currents will continue along many north- and east- facing beaches of Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands through much of the forecast period. Beachgoers should swim near lifeguards and follow beach warning flags.

Short Term(Today through Sunday)

Issued at 355 AM AST Fri May 15 2026

In general, a surge of moisture brought showery weather, especially across St Croix, and PR's windward locations, but with the best activity over the southern USVI and surrounding waters. This activity produced periods of moderate to locally heavy rain, reducing visibility and creating water puddles across roadways and poorly drained areas. Low temperatures ranged from the mid-70s to the low-80s at urban and coastal sites, to the low and upper-60s at mountain sites. The winds were primarily from the east to east- southeast at 10 to 15 mph, with stronger gusts in windward locations, while leeward sites experienced 5 to 10 mph, with fluctuations in the land breeze also observed.

A mid- to upper-level ridge will continue to dominate the region through Saturday, helping to limit widespread thunderstorm development. However, breezy east-to-east-southeast winds will continue to move patches of moisture across Puerto Rico and the U.S. Virgin Islands, resulting in periods of showery weather with moderate to locally heavy rainfall at times. Because of this pattern, a limited risk of flooding will remain across windward areas of Puerto Rico and the U.S. Virgin Islands, particularly during the overnight and morning hours. During the afternoons, local effects, sea breeze convergence, and daytime heating will support the development of showers across interior and western Puerto Rico.

This overall weather pattern is expected to persist through Friday and Saturday, with little to no thunderstorm activity anticipated. However, by Sunday, the ridge is forecast to weaken as a mid- to upper-level trough approaches from the west. This will increase instability and improve the chances of thunderstorm development across the region.

Model guidance also suggests low- to mid-level vorticity moving across the area, which could help enhance shower and thunderstorm development, especially early Sunday morning across the U.S. Virgin Islands and eastern Puerto Rico. Additional afternoon and evening thunderstorm activity may then develop across interior and western Puerto Rico due to strong daytime heating, local terrain effects, and sea breeze interactions. As a result, the flooding risk is expected to increase on Sunday, especially across interior and western Puerto Rico, where urban flooding, road ponding, and isolated small-stream flooding may occur. Residents and visitors should continue monitoring forecast updates as the weather pattern evolves.

Although rain is expected each day, above-normal temperatures will continue across the region. Model guidance indicates warmer- than-normal temperatures at low levels of the atmosphere, while sea surface temperatures surrounding the islands remain near or above 1C above normal. Combined with available moisture, these factors will continue to produce elevated heat indices across Puerto Rico and the U.S. Virgin Islands.

At this time, a Heat Advisory has not been issued because patches of cloud cover and passing showers may help limit the duration of the hottest conditions in some areas. Nevertheless, residents and visitors can still expect heat indices up to 111F each day, especially between 10 AM and 4 PM across urban and coastal areas. People are encouraged to stay hydrated, limit prolonged sun exposure, and take frequent breaks if spending time outdoors.

In addition, traces of Saharan dust particles will begin moving into the region over the next couple of days. The highest concentrations are expected to remain south of the islands across the Caribbean Sea, although slight increases in hazy conditions are possible by Saturday. By Sunday afternoon, most of the dust is expected to clear from the area, leaving only trace amounts that could still act as condensation nuclei and support cloud development.

Long Term(Monday through Friday)

Issued at 355 AM AST Fri May 15 2026

A gradual transition toward a wetter weather pattern is expected across Puerto Rico and the U.S. Virgin Islands through the upcoming workweek. Surface high pressure over the western Atlantic will maintain easterly winds early in the period, gradually veering east- southeasterly by midweek while weakening from fresh to strong speeds to more moderate to locally fresh conditions late in the week. Although moisture levels early in the period should remain near to slightly below seasonal normals, patches of deeper tropical moisture moving across the region will continue to promote passing showers across eastern Puerto Rico and the U.S. Virgin Islands during the overnight and morning hours, followed by afternoon convection across western Puerto Rico.

At upper levels, model guidance continues to indicate an amplifying trough north of the northeastern Caribbean, with marginally cooler mid-level temperatures gradually spreading closer to the local islands through mid to late week. At the same time, mid-level conditions are forecast to become less dry, allowing for a somewhat more favorable environment for shower development. As precipitable water values gradually increase to near and occasionally above normal levels, shower activity is expected to become more frequent by Wednesday and Thursday, particularly across western and northwestern Puerto Rico and portions of the San Juan metropolitan area. Although thunderstorms were not explicitly introduced into the forecast at this time, excessive diurnal heating combined with the more favorable thermodynamic environment may support one or two very isolated thunderstorms during the afternoon hours. Hazard risks remain at medium confidence, primarily associated with localized excessive rainfall and excessive heat, as warm to hot daytime temperatures and elevated humidity levels will likely continue through much of the period.

AVIATION

(06Z TAFS) Issued at 355 AM AST Fri May 15 2026

Expect VFR conditions through much of the forecast period. However, the advection of SHRA/-SHRA will continue to arrive affecting windward terminals from time to time. Additional SHRA/+SHRA will form across the interior and NW-PR btwn 15/16-23z, probably affecting JBQ and JSJ, which could cause brief MVFR or IFR conds. Winds will prevail from the E-ESE around 10 kt, then aft 15/13z winds will range btwn 10-20kt with higher gusts and sea breeze variations.

MARINE

Issued at 355 AM AST Fri May 15 2026

A broad surface high-pressure over the central Atlantic will continue to promote moderate to locally fresh east to east- southeasterly winds across the regional waters. These breezy conditions will maintain somewhat choppy seas, particularly across the offshore and exposed Atlantic and Caribbean waters. Seas are forecast to remain between 4 and 5 feet, occasionally up to 6 feet, through at least the upcoming weekend.

BEACH FORECAST

Issued at 355 AM AST Fri May 15 2026

Moderate rip current risk will prevail from Friday onwards along the northern and eastern beaches of PR, as well as Culebra, Vieques, and the US Virgin Islands. The long period northerly swell should gradually subside tonight allowing conditions to gradually improve. Nevertheless, beachgoers should continue exercising caution especially near piers and unprotected beaches.

SJU WATCHES/WARNINGS/ADVISORIES

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