textproduct: San Juan

KEY MESSAGES

Issued at 205 PM AST Sat Jun 6 2026

* Hot and humid conditions will continue through much of the forecast period, with heat indices between 100 and 110F or higher in the USVI and PR urban and lower-elevation areas. Take precautions if spending extended time outdoors.

* Afternoon showers and isolated thunderstorms are expected, especially this weekend, mainly across the interior and northwestern portions of Puerto Rico. Localized heavy rainfall may lead to ponding on roads, poor drainage, and even isolated urban flooding.

* A weak tropical wave will move across the region early Sunday, increasing shower activity and the potential for isolated thunderstorms. However, abundant dry air and Saharan dust should limit the risk of widespread flooding.

* Saharan dust will increase Sunday evening into early next week, resulting in hazy skies, reduced air quality, occasional visibility reductions, and a decrease in overall rainfall activity.

* Life-threatening rip currents are possible throughout much of the forecast period. Breezy to locally windy east-southeast winds could result in life-threatening rip currents mainly along the east and north coast of PR and the USVI.

Short Term(This evening through Monday)

Issued at 205 PM AST Sat Jun 6 2026

Another warm-to-hot day across Puerto Rico and the U.S. Virgin Islands due to an east-southeast wind flow, above-normal temperatures, and the available moisture. Heat indices ranged from 100 to 110 degrees Fahrenheit, with higher values in urban and poorly ventilated areas. Thus, a Heat Advisory was issued. Traces of Saharan dust particles are still over the region. Winds were generally 10 to 20 mph across the coastal sites, with local gusts higher. Temperatures were in the upper 80s to lower 90s across the USVI and PR's coastal and urban areas.

For this afternoon, in addition to the above-normal heat indices, we expect showers to develop mainly along the interior and northwest quadrant of PR. Also, streamer-like showers could form downwind from the USVI and La Sierra de Luquillo. Additionally, isolated thunderstorms enhanced by sea breezes cannot be ruled out today, mainly across the northwest quadrant. Therefore, there is still potential for heavy rainfall, leading to roadway ponding or even urban flooding. Most of the region will experience partly to variably cloudy skies and warmer-than-normal temperatures.

Tonight through Sunday morning, warmer-than-normal minimum temperatures are anticipated. A weak tropical wave will swing by the islands around early Sunday morning, increasing passing showers across the local waters, with some moving inland over the USVI and PR. The tropical moisture associated with this perturbation will remain near normal, promoting a seasonal weather pattern through Sunday afternoon. Due to abundant dry air and Saharan dust surrounding the wave, the potential for widespread flooding is limited. Even so, localized ponding of water, urban flooding, and a few stronger thunderstorms cannot be ruled out, particularly during the afternoon hours across the interior and western Puerto Rico. Behind the wave, Saharan Air Layer is expected to arrive Sunday evening and persist into early next week, resulting in hazy skies, reduced visibility at times, and a return to more limited rainfall activity.

The wind flow will mainly continue from the east to east- southeast, with warmer-than-normal temperatures.

Long Term(Tuesday through next Friday)

Issued at 357 AM AST Sat Jun 6 2026

No major changes were introduced to the long-term forecast. A surface high pressure over the Central Atlantic will maintain easterly winds through Thursday, veering from the southeast by Friday. Pressure gradient will remain weak due to the interaction between the high and a low pressure in the northern Atlantic, slightly weakening winds. Nevertheless, the high should strengthen by the end of the period, increasing the pressure gradient once again and resulting in breezy conditions across the islands. A drier and stable weather pattern will likely dominate on Tuesday and Wednesday as light to moderate concentrations of Saharan Dust will persist on Tuesday afternoon and a drier air mass filtering into the region on Wednesday, limiting shower activity. From the latest model guidance, PWAT values may drop to below climatological normal (between 1.25 and 1.5 inches), with moisture content in the low and mid levels plummeting as well (between 20 and 40 %). Additionally, warmer-than-normal mid-level temperatures (500 mb temperatures above -6 degrees Celsius) which makes it unfavorable for deep convection. Although diurnal heating, local effects, and sea breeze convergence should allow afternoon convection on both days, it will likely remain shallow, presenting a low potential for urban and small stream flooding. By Thursday, guidance suggests an increase in tropical moisture associated with a tropical wave likely to move across the Caribbean Basin, south of the CWA. From the latest deterministic solutions, both GFS and ECMWF show an increase in PWAT values (between 1.6 and 1.8 inches), typical for this time of the year. From a probabilistic perspective, ensemble members tend to wetter solutions, with a low chance of reaching 2.0 inches. Additionally, an upper-level trough deepening into the tropics will gradually cool mid-level temperatures (around -7 degrees Celsius), introducing instability aloft and enhancing deep convection. For this particular scenario, showers will likely move across the U.S. Virgin Islands and portions of eastern Puerto Rico during Thursday morning, while afternoon convection will likely concentrate over interior and western/northwestern Puerto Rico. Showers and isolated thunderstorms will likely lead to ponding of water over roadways and poorly drained areas, along localize minor flooding. As the tropical wave continues to move across the Caribbean Basin, another drier- than-normal airmass will filter into the region, reducing the chance of precipitation on Friday.

The latest model guidance suggests typical warmer-than-normal 925 mb temperatures during the long-term forecast. This, combined with the available moisture, will result in heat indices exceeding 100 degrees Fahrenheit, increasing heat risk across urban areas and low elevations across the islands. Hence, residents and visitors must exercise caution, as these heat levels can affect individuals sensitive to heat, particularly those without effective cooling and/or adequate hydration. A Heat Advisory, particularly on Thursday, may be required.

AVIATION

(18Z TAFS) Issued at 205 PM AST Sat Jun 6 2026

Mainly VFR conds across TAF sites. E-ESE winds will continue around 10 to 16 kts with occasionally higher gusts. SHRA/TSRA area possible across TJBQ and promote brief MVFR conds thru 06/22Z. ESE Winds will decrease to around 10 kts after 06/23Z, increasing again after 07/13Z. Passing SHRA and VCSH will continue to reach windward sectors of PR and USVI from time to time tonight. HZ will likely cause VIS reductions from tomorrow morning onward.

MARINE

Issued at 205 PM AST Sat Jun 6 2026

An Atlantic high-pressure system will maintain a tight pressure gradient across the northeastern Caribbean through much of the forecast period, supporting moderate to fresh east-southeast winds and choppy seas across the regional waters, especially the offshore Atlantic waters and Caribbean Passages. A weak tropical wave will cross the local islands early Sunday morning, increasing shower activity and the potential for isolated thunderstorms. Hazy skies associated with a Saharan Air Layer will persist across the region, though marine visibilities should generally remain at 6 nautical miles or greater.

BEACH FORECAST

Issued at 205 PM AST Sat Jun 6 2026

There's still potential for life-threatening rip currents along the exposed beaches, mainly due to breezy to locally windy east- southeast winds. This risk will continue through at least the middle of next week. Therefore, beachgoers are urged to exercise caution, remain aware of surf conditions, and avoid venturing too far from shore, as life-threatening rip currents are possible across most of the region.

FIRE WEATHER

Issued at 357 AM AST Sat Jun 6 2026

RH % values for today are forecast to remain slightly above the threshold limiting the weather conditions to favor widespread fire danger threat along southern coastal plains. Winds will remain from the southeast up to 15 mph with gusty winds along coastal zones. Based on the forecast weather conditions, we expect a low fire danger risk. Please stay tune for further updates.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007- 008-010>013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...None.