textproduct: San Juan

KEY MESSAGES

Issued at 139 PM AST Wed Jul 8 2026

* Drier air, accompanied by moderate to high concentrations of Saharan dust, will spread across the region, particularly from tomorrow through the weekend. This will result in hazy skies, reduced visibility, and degraded air quality.

* Breezy to windy easterly winds will persist through much of the period. Hazardous conditions for small craft are present across portions of the local waters, while a moderate risk of rip currents persists along many local beaches.

* Warm to hot conditions will continue. Heat concerns will increase from late this week into early next week, while the drier conditions will also elevate the risk of fire spread.

* The next increase in tropical moisture and shower activity is expected early next week as another tropical wave moves across the region.

Short Term(This evening through Friday)

Issued at 139 PM AST Wed Jul 8 2026

The morning and early afternoon weather conditions remained variable due to the presence of a moisture field associated with a tropical wave moving westward into and out of the region. In the early morning hours, showers were observed across eastern municipalities extending into the northcentral areas and the San Juan metro area. As the day progressed, showers persisted and moved across the rest of the northern coastal areas and across the local waters, with heavy showers and thunderstorm activity across the offshore Atlantic waters. So far as 12 PM, rainfall activity reported by estimates from radar fluctuated between half to one inch, with higher accumulations of 1.5 inches across southeastern central sections. Daytime temperatures remained in the upper 80s across the coastal areas and urban areas, increasing up to the lower 90s across southwestern sections of Puerto Rico. Related to those observed values, heat indices across the region remained mostly in the 99 to 102 degrees, slightly higher across some isolated areas, including the north-central sections, with values of heat indices rounding 103 to 104 degrees F.

For the rest of the afternoon, shower conditions will continue across western interior sections due to decent moisture values across the area with precipitable water values of 1.8 in according to derived satellite imagery data. Therefore, residents can expect periods of showers across the western interior from Las Marias moving into the Mayaguez area and vicinity areas. The 08/12Z sounding showed 6 degrees at 500MB, which may increase in some way the potential of observed one or two isolated thunderstorms with the heaviest activity of showers from 2 PM to 4PM. In general, after that period, weather conditions are forecast to gradually change as a much drier airmass moves into the region with precipitable water of 1.6 inches. Additionally, an increase in Saharan Dust particles is forecast across the region starting this afternoon across the U.S Virgin Islands and eastern Puerto Rico, then extending into the rest of the CWA by later tonight into the early hours of Thursday. Having said that, Thursday looks quite dry with minimal values of moisture across the region. However, instability aloft will remain present, and colder temperatures at 500 MB are expected to round to -9 degrees as suggested by the GFS model guidance. According to the Glvez-Davison Index (GDI), Thursday had decent chances to observe thunderstorm activity, but limited coverage of showers is expected due to limited moisture in the mid levels. For Friday, dry conditions will remain in place due to the Saharan dust in the area.

Warmer conditions are expected to be present from Thursday into Friday, with heat indices reaching 108 degrees and slightly warmer across northern and central sections and southwestern sections. Residents are urged to stay hydrated and pay attention to the vulnerable communities during the peak of the heat between 10 AM and 2 PM AST.

Long Term(Saturday through Wednesday)

Issued at 145 AM AST Wed Jul 8 2026

Saharan Dust and stable conditions will likely persist this upcoming weekend, though moisture content should increase early next week. As mentioned in the previous discussion, the wind pattern will likely be dominated by a series of surface high pressures, with winds veering from the E-ESE for most of the period. Although the local pressure gradient may weaken by Sunday, winds should remain seasonal, with breezy to locally windy conditions throughout the forecast period. Shower activity should remain limited on Saturday and Sunday, as model guidance continues to suggest drier-than-normal conditions (PWAT values between 1.2 and 1.4 inches), with dry slots in the low and mid levels. Additionally, a dense, broad plume of SAL will continue to filter into the region, with moderate and high concentrations across the CWA. These conditions will likely result in hazy skies, reduced visibility, and deteriorated air quality. Although daytime heating, local effects, and sea breeze convergence may induce convection, any shower development should remain fast- moving and short-lived, with low rainfall accumulations. A weak tropical wave should approach the Caribbean Basin, pooling tropical moisture into the region, through global model solutions disagree in the time of arrival of the system. The ECMWF shows abundant moisture content approaching late Sunday night into early Monday, while the GFS continues to suggest more shower activity by Monday afternoon into the evening. Although the long-term forecast is tending more to the latest GFS solutions and NBM suggestions, theres uncertainty regarding the TOA and any shower activity related to the tropical wave. Variability remains high as Saharan Dust concentrations persist across both the Atlantic and Caribbean Basin, according to the latest NASA GEOS Dust AOT, which may weaken the tropical wave. The weather pattern on Tuesday and Wednesday will be similar to Saturday and Sunday, with drier and more stable conditions across the islands.

In terms of heat, seasonal temperatures combined with available moisture will lead to heat indices reaching and exceeding 100 degrees Fahrenheit, particularly over urban and low-lying areas of the islands. As mentioned in previous discussions, the presence of Saharan Dust will likely continue to inhibit nighttime cooling, with warmer minimum temperatures. Therefore, the heat threat will likely remain elevated throughout the forecast period.

AVIATION

(18Z TAFS) Issued at 139 PM AST Wed Jul 8 2026

VFR conditions will remain in place across all TAF sites. VIS reduction is forecast due to Saharan dust particles arriving in the region today through tomorrow. Winds will continue from the E up to 18 knots with gusty winds, diminishing at 08/23Z, increasing again at 09/14Z up to 18 knots during the day.

MARINE

Issued at 139 PM AST Wed Jul 8 2026

A broad surface high pressure over the central Atlantic will maintain moderate to fresh east to east- southeast winds, occasionally strong, along with choppy to hazardous seas through the end of the workweek. Small Craft Advisories remain in effect through at least late Friday night due to a combination of seas up to 7 feet and easterly winds of 20 to 25 knots across the Atlantic and Caribbean waters, including the Mona Passage. In the wake of the tropical wave that produced showers and isolated thunderstorms earlier today, a drier air mass will move into the region later this afternoon. Moderate to high concentrations of Saharan dust will then overspread the area, resulting in hazy skies and reduced visibility through the rest of the week and into the weekend.

BEACH FORECAST

Issued at 139 PM AST Wed Jul 8 2026

Wind-driven seas and breezy conditions will maintain a moderate risk of rip currents across most beaches of Puerto Rico and the U.S. Virgin Islands through the rest of the week and into the weekend. This means that life-threatening rip currents will remain possible in the surf zone. Beachgoers are encouraged to remain cautious. Additional beach hazards include the presence of Saharan dust, which will result in hazy skies, reduced air quality, and warm to hot conditions during the peak heating hours of the day. An elevated heat threat will persist on most days, with heat indices ranging from 100F to 110F across most coastal areas, particularly along the northern, western, and southern coastlines of Puerto Rico.

FIRE WEATHER

Issued at 139 PM AST Wed Jul 8 2026

The departure of a tropical wave will maintain slightly higher low-level moisture today, limiting fire weather concerns despite breezy to locally windy easterly trade winds. However, critically dry vegetation and persistent soil moisture deficits will continue to support wildfire development, and any ignition could still spread through the available fine fuels. By Thursday, below-normal moisture, moderate to high concentrations of Saharan dust, and increasingly dry conditions will overspread the region, while breezy to windy trade winds persist. This combination will become more favorable for wildfire growth through the end of the workweek and into the weekend. Residents and visitors should avoid outdoor burning and exercise extreme caution with any activity capable of producing sparks or open flames.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...Small Craft Advisory until midnight AST Friday night for AMZ711- 733-741.

Small Craft Advisory until midnight AST tonight for AMZ712-735.