textproduct: San Juan

KEY MESSAGES

Issued at 313 PM AST Tue Jul 7 2026

* A weak tropical wave will move across the region on Wednesday, promoting isolated to scattered showers and t-storms, mainly across portions of Puerto Rico and the U.S. Virgin Islands.

* Warm conditions will persist through the remainder of the week, with peak heat indices ranging from 100F to 110F across lower elevations.

* Another surge of Saharan dust is expected to arrive Wednesday and persist into Thursday, leading to increased haze and reduced air quality across the forecast area.

* A moderate risk of rip currents is expected to continue along many of the local beaches over the next several days. In addition, a drier air mass will settle over the northeastern Caribbean from Thursday into Friday, increasing the potential for elevated fire weather conditions, particularly across southern and western Puerto Rico.

Short Term(This evening through Thursday)

Issued at 313 PM AST Tue Jul 7 2026

Variable to showery weather conditions prevailed throughout the morning as a slight increase in low-level moisture promoted passing showers across eastern sections of Puerto Rico. Despite the available moisture, rainfall activity remained mostly on the limited side. Hazy skies were widely observed across all the islands due to the continued presence of suspended Saharan dust particulates. Furthermore, temperatures warmed quickly, causing heat index values to rapidly increase; coastal sections reported indices between 90 and 94 F as early as 8 AM, eventually reaching the 100s to locally around 110 F at 1 PM. Widespread heat index values in this range then decreased as rainfall, t-storm and cloud coverage increased. By 2:40 PM, rainfall accumulations reached 2.29 in over Mayaguez, up to 1.40 over the eastern interior, up to an inch over eastern Puerto Rico and around three quarters of an inch over Culebra. Breezy conditions also persisted throughout the morning, with sustained winds remaining generally from the east at around 15 to 25 mph, accompanied by higher gusts across coastal areas.

For the rest of today and into Wednesday, the local weather pattern will be influenced by the arrival of a weak tropical wave and the persistence of upper-level troughing. Hazy conditions will begin to gradually decrease after 6 PM as moisture and cloudiness associated with the approaching wave invade the local region. Aloft, a deep- layer low-pressure system centered at the 250 mb level will maintain considerable upper-level cloudiness across the area. This widespread cloud cover will limit radiational cooling tonight, resulting in warm overnight temperatures that are forecast to remain 1 to 2 degrees above climatological normals. While this upper-level low will continue to promote colder temperatures at the 500 mb level near the area, drier conditions entrenched at the mid-levels will effectively inhibit the development of deep, well-organized convective showers. Nevertheless, as the wave pushes through, the latest high-resolution model guidance suggests an increase in showers across the U.S. Virgin Islands and eastern sections of Puerto Rico from late tonight into Wednesday morning. Recent GOES satellite imagery indicates precipitable water values hovering around 1.88 inches, and this elevated moisture will persist throughout the day on Wednesday. This low-level moisture will combine with local effects and daytime heating to enhance localized afternoon convection across western Puerto Rico. However, overall shower activity is forecast to remain on the limited side due to the inherent weakness of the tropical wave and the residual Saharan dust intrusion that preceded the system.

By Thursday, local weather conditions are expected to change once again as the bulk of the tropical moisture field moves out of the region. This will give way to a much drier and more stable air mass, resulting in a significantly reduced chance for shower development across the islands. Accompanying this drier air will be another pulse of Saharan dust particulates. Current guidance suggests this incoming dust will arrive in moderate concentrations, which will quickly reintroduce hazy skies and reduced visibility across the forecast area. As a result, residents should expect predominantly fair but hazy weather for Thursday, with precipitation severely limited as the dusty, stable environment effectively suppresses convective activity.

Long Term(Friday through next Monday)

Issued at 134 AM AST Tue Jul 7 2026

Dry and mostly stable conditions are expected through the upcoming weekend and into early next week. A surface high north of the region will maintain generally east to east-southeasterly winds, with a brief shift to the northeast possible on Sunday due to an induced surface trough. Another surface high over the central Atlantic will strengthen the easterly flow again by early next week.

A drier air mass and moderate to high concentrations of Saharan dust will continue filtering into the region, limiting shower activity. Both the GFS and ECMWF indicate precipitable water values falling below climatological normals through the weekend, while forecast soundings show an unusually dry lower atmosphere. Although an upper-level low may linger nearby, the environment should remain unfavorable for sustained convection. Any showers that develop will be brief, fast-moving, and produce minimal impacts.

Hazy skies, reduced visibility, and degraded air quality will persist as Saharan dust continues across the region. Meanwhile, above-normal temperatures and sufficient low-level moisture will maintain dangerous heat, with heat indices likely exceeding 102F across urban, coastal, and lower-elevation areas. Warm overnight temperatures will provide little relief, allowing cumulative heat stress to persist into early next week.

AVIATION

(18Z TAFS) Issued at 313 PM AST Tue Jul 7 2026

Mainly VFR conditions Moderate concentrations of Saharan dust will continue to produce HZ and occasional VIS reductions, gradually improving overnight. -SHRA/VCSH will continue during the afternoon and evening hours across most terminals with -VCTS possible mainly at PR terminals. Although a break in coverage is forecast tonight, an approaching tropical wave will once again increase shower frequency late overnight into tomorrow. Moderate concentrations of HZ will accompany this wave. E-ESE winds up to 16-24 kt with higher gusts, diminishing to 8 to 14 kt after 07/22Z.

Brief VCSH are possible near TJSJ and TJBQ between 07/16-22Z, then near TJSJ and the USVI terminals after 07/22Z. E-ESE winds will increase from 6-12 kt to 16-22 kt with higher gusts between 07/13-22Z, diminishing to 8-14 kt after 07/22Z.

VFR conditions will prevail at all TAF sites. Moderate to locally high concentrations of Saharan dust will continue to produce HZ and occasional VIS reductions, gradually improving overnight ahead of an approaching tropical wave. Brief VCSH are possible near TJSJ and TJBQ between 07/16-22Z, then near TJSJ and the USVI terminals after 07/22Z. E-ESE winds will increase from 6-12 kt to 16-22 kt with higher gusts between 07/13-22Z, diminishing to 8-14 kt after 07/22Z.

MARINE

Issued at 313 PM AST Tue Jul 7 2026

The marine forecast remains on track. A broad area of high pressure over the central Atlantic will maintain moderate to locally fresh easterly to east-southeasterly winds, resulting in choppy marine conditions through the next several days. A fast- moving tropical wave will increase the potential for isolated thunderstorms across the Caribbean waters from this evening through Wednesday. Thereafter, from Thursday into the weekend, thunderstorm activity is expected to diminish significantly as moderate to high concentrations of Saharan dust overspread the region, promoting a drier and more stable air mass that will limit shower and thunderstorm development.

BEACH FORECAST

Issued at 313 PM AST Tue Jul 7 2026

Beach conditions will remain hazardous through the end of the workweek as moderate to fresh easterly winds maintain a moderate risk of rip currents across most local beaches. Dangerous heat will continue each afternoon, with peak heat indices between 100F and 110F increasing the risk of heat-related illnesses for beachgoers. A few thunderstorms are possible on Wednesday as a fast-moving tropical wave crosses the region. Beach visitors are encouraged to stay hydrated, seek shade frequently, avoid prolonged sun exposure during the hottest part of the day, and move indoors immediately if thunderstorms develop.

FIRE WEATHER

Issued at 134 AM AST Tue Jul 7 2026

Higher humidity and a passing tropical wave will make weather conditions less supportive of rapid wildfire growth through Wednesday. Nevertheless, critically dry vegetation and persistent soil moisture deficits will continue to favor wildfire development, and any ignition could still spread through the available fine fuels despite fire weather thresholds not being met. As drier air and Saharan dust return late Wednesday into Thursday, weather conditions will once again become more favorable for wildfire growth through the end of the workweek. Residents and visitors should avoid outdoor burning and use extreme caution with any activity capable of producing sparks or open flames.

SJU WATCHES/WARNINGS/ADVISORIES

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