textproduct: San Juan

KEY MESSAGES

Updated at 150 AM AST Thu May 7 2026

* A warm to hot weather pattern will continue through the weekend, especially across urban and coastal areas of all the islands.

* Passing showers increase today across the USVI, with locally heavy showers developing over western PR this afternoon.

* Mostly fair weather conditions will prevail through the second week of May across the islands, with the exception of diurnally induced afternoon showers over western PR each day.

* Beachgoers can expect a moderate rip current risk to continue along the north and east-facing beaches throughout much of the forecast period.

Short Term(Today through Saturday)

Issued at 150 AM AST Thu May 7 2026

Showers increased overnight from the Anegada Passage into the Caribbean waters in response to an upper-level trough crossing the region form west to east. Short-lived isolated thunderstorms were observed just east of the USVI, with showers moving over coastal areas of the islands, leaving between a quarter to half an inch of rain. The St. John RAWS station in the eastern side of the island reported 0.66 inches. Also, weak but persistent showers were noted over NW PR, where the Doppler radar estimated close to 0.20 inches in Moca. For the rest of the morning hours, hi-res and global model guidance indicates that showers will develop between the USVI and eastern PR, followed by stronger afternoon convection over the western interior of PR as precipitable water (PWAT) content remains on the lower bound of the 50th percentile near 1.60 inches, and due to the proximity of the trough.

From tonight through the rest of the short term period, mid- level ridging begins to build over the northeastern Caribbean as the upper-level trough moves further into the Leeward Islands. Model guidance suggest that PWAT values will hover between 1.20-1.50 inches, which is in the 25th percentile for early May. Despite the presence of the departing upper-level trough, the 500mb temperatures are forecast to warm near 5C, and a persistent dry layer btw 700-500mb with RH values dropping below 30% will provide significant subsidence and entrainment, limiting convective vertical growth. Therefore, a relatively stable weather pattern is expected with light passing overnight and early morning showers across the windward areas of the islands, followed by shallow afternoon convection over the interior and western sections of PR driven by diurnal heating and the sea breeze convergence.

Looking at the broader scale, the latest Madden-Julian Oscillation forecast shows the region transitioning into a suppressed phase, which supports increasing atmospheric stability and drier than normal conditions through the weekend. Overall, heat remains a primary concern, as southeast winds today and the brief surge in moisture push daytime highs in the upper 80s and low 90s across coastal and urban areas, with heat indices likely reaching the 102-107F range. Although winds turn more ENE on Fri-Sat, the 925mb temperatures are still forecast to range between 21-22C which is in the 75th percentile.

Long Term(Sunday through Thursday)

Issued at 150 AM AST Thu May 7 2026

A predominantly stable weather pattern will prevail through midweek as a mid-level ridge remains anchored over the northeastern Caribbean. This will continue to promote subsidence and maintain a drier-than-normal environment, with available moisture largely confined below 700 mb. As a result, vertical development will be limited, favoring mostly fair weather conditions across the region. Model guidance remains in good agreement, showing little deviation from this pattern through the period.

At the surface, an east to east-southeasterly flow will dominate, supporting a typical trade wind pattern. Brief, fast-moving showers will affect windward areas during the overnight and early morning hours, followed by isolated to locally scattered afternoon convection over interior to western Puerto Rico, driven by local effects and possibly enhanced by intense diurnal heating. However, overall rainfall coverage will remain limited, and thunderstorm development is expected to be minimal.

The main hazards during this period will be heat and breezy conditions. Above-normal temperatures combined with warm low-level moisture will promote a limited heat risk each day, particularly for sensitive individuals or those engaging in prolonged outdoor activities without adequate hydration. In addition, breezy conditions will persist, especially across exposed coastal and windward areas, leading to a limited non-thunderstorm wind risk with occasional gusts around or above 25 mph. The combination of these factors may support an elevated fire danger risk, particularly across southern and coastal Puerto Rico where fuels will continue to dry.

AVIATION

(06Z TAFS) Issued at 150 AM AST Thu May 7 2026

Mainly VFR conditions are expected to prevail across all terminals through the fcst period. However, SHRA could lead to brief MVFR conds across the USVI terminals thru 07/10z. Locally induced SHRA downwind of the mountain ranges of PR should cause mostly VCSH with brief -RA periods btw 07/16-22z. ESE winds increasing 12-16 kt early this morning before backing fm the ENE aft 07/18z.

MARINE

Issued at 150 AM AST Thu May 7 2026

A series of broad surface highs and frontal lows over the Atlantic will promote moderate east to east-northeast winds through at least Sunday. By the weekend, winds are expected to increase to moderate to fresh levels across the regional waters. Seas will range between 2 and 4 feet, occasionally higher due to the combination of local wind waves and a few pulses of a small, long-period northeasterly swell spreading across the Atlantic waters.

BEACH FORECAST

Issued at 150 AM AST Thu May 7 2026

A moderate risk of rip currents is forecast to continue along the north and east-facing beaches throughout the forecast period. A low risk of rip currents will continue elsewhere. Beachgoers are encouraged to exercise caution, as beaches with low risk could develop life-threatening rip currents in the vicinity of groins, jetties, reefs, and piers. For additional information, visit: weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

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