textproduct: San Juan

KEY MESSAGES

Updated at 156 PM AST Mon May 4 2026

* Locally induced isolated showers over eastern and northwestern Puerto Rico this afternoon.

* An approaching trough Tuesday and Wednesday may support localized afternoon showers, with brief heavy rainfall possible. Isolated thunderstorms cannot be ruled out, though activity will remain limited.

* Warmer-than-normal temperatures will persist across Puerto Rico and the U.S. Virgin Islands, with heat indices reaching or exceeding 100F across urban and coastal areas.

* Mainly a moderate rip current risk will continue along north and east-facing beaches of the islands at times.

Short Term(This evening through Wednesday)

Issued at 156 PM AST Mon May 4 2026

Overall, mostly calm weather conditions prevailed today across Puerto Rico and the U.S. Virgin Islands, with mostly clear to partly cloudy skies observed through much of the day. Temperatures along coastal areas remained in the upper 80s to low 90s, while interior and higher elevations ranged from the upper 70s to mid 80s. Winds were predominantly from the southeast, contributing to warm and somewhat humid conditions across the islands, which allowed heat indices to reach 100 degrees Fahrenheit in those urban areas.

For the rest of today into tonight, we anticipated limited to no rainfall activity, meaning that tranquil weather conditions are expected to continue under a relatively stable pattern. Partly cloudy skies will prevail, with only isolated, brief passing showers possible across windward areas and surrounding waters. Overnight temperatures will remain warm, generally in the upper 70s along the coast and upper 60s across higher terrain.

By Tuesday and Wednesday, winds area forecast to slightly increase and become a bit more dynamic as a polar trough and its associated frontal boundary approaches the region from the western Atlantic. Although the boundary is expected to remain north of the area, its proximity combined with surface high pressure over the central Atlantic will help maintain a southeasterly wind flow across the region. Precipitable water values are forecast to increase slightly, with additional patches of low-level moisture advected into the area, but mainly over the waters, as persistent mid-level drying continues to inhibit widespread deep convection.

Temperatures will remain above normal through the short-term period, supported by a warm airmass advected by southeasterly flow. This will promote heat indices reaching or slightly exceeding 100 degrees F, especially across coastal and urban areas, resulting in a limited heat risk. These conditions will mainly impact heat-sensitive individuals, particularly those exposed to outdoor conditions without adequate hydration or effective cooling.

Long Term(Thursday through Monday)

Issued at 244 AM AST Mon May 4 2026

A transition toward a drier pattern is expected during the mid to late week period, particularly from around May 7 through May 10, as moisture decreases and subsidence strengthens across the region. This will lead to a noticeable reduction in shower activity and overall rainfall coverage. Temperatures will gradually rise under this pattern, supporting a limited heat risk, mainly affecting sensitive individuals exposed to prolonged outdoor conditions without adequate hydration or cooling.

Breezy conditions will continue, especially during the first half of the period, with easterly winds occasionally reaching locally fresh levels. This will result in a limited non-thunderstorm wind risk, with gusts around 20 to 25 mph possible at times, particularly across coastal and windward areas. While impacts remain minor, unsecured objects may be blown around, and these conditions could contribute to localized hazard enhancement when combined with drying conditions.

A secondary concern will be the potential for elevated fire danger. The combination of reduced rainfall, increasing temperatures, and breezy winds will promote the drying of fine fuels. In addition, Keetch-Byram Drought Index (KBDI) values exceeding 600 indicate increasingly dry soil conditions. These factors suggest that fire danger may increase across portions of the region, particularly across southern and windward coastal areas. Conditions will continue to be monitored for any further increase in fire weather risk.

AVIATION

(18Z TAFS) Issued at 156 PM AST Mon May 4 2026

VFR condt are expected to prevail across all terminals. VCSH possible over TJSJ, TIST, TISX after 04/18Z. Winds will remain around 12kts with occasional higher gusts, becoming light and variable overnight.

MARINE

Issued at 156 PM AST Mon May 4 2026

A broad high pressure over the central Atlantic will maintain an easterly to southeasterly flow over the forecast period. Winds will remain generally gentle to moderate, around 10 to 15 knots, with periods of locally fresh winds across the Atlantic waters and Anegada passage at times. Seas will range between 2 and 4 feet, occasionally up to 5 to 6 feet due to a combination of local wind waves and a few pulses of a small, long-period northeasterly swell spreading across the Atlantic waters. Overall conditions will remain favorable for small craft, though operators should exercise caution at times due to wind-driven seas and passing showers that may produce locally higher winds and seas.

BEACH FORECAST

Issued at 156 PM AST Mon May 4 2026

Pulses of small, long-period northeasterly swell will occasionally promote higher breakers and stronger rip currents. As a result, a moderate risk of rip currents will continue across the north- and east-facing beaches of Puerto Rico through much of the workweek. Across the U.S. Virgin Islands, the risk will be moderate at times along St. Croix and mainly low along St. Thomas and St. John. By Friday, conditions are expected to gradually improve, with a low risk briefly prevailing across most beaches, then a moderate risk returning by the weekend. For additional information and location- specific rip current details, visit weather.gov/beach/sju.

FIRE WEATHER

Issued at 156 PM AST Mon May 4 2026

A Fire Danger Statement (RFDSJU) was issued early this morning for today. As anticipated, no rainfall have been seen across the southern sections of Puerto Rico today and drier air mass over the region is allowing relative humidity values to drop into critical fire weather thresholds. As of 1:30 PM AST, the Cabo Rojo and Guanica RAWS stations have been registering RH values in the low 50s and winds speeds in around 10 to 18 mph, with gust around 20 to 27 mph. KBDI values in Cabo Rojo remain above critical fire weather thresholds. Additionally, the 7-day percent of normal rainfall across the southeastern coastal plain, including areas near Salinas, is below 25%, with some locations even below 5%. Therefore, conditions remain favorable for the spread of wildfires along the southern coastal plains of Puerto Rico.

SJU WATCHES/WARNINGS/ADVISORIES

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