textproduct: San Juan

KEY MESSAGES

Issued at 322 AM AST Thu Jun 25 2026

* High, to locally very high, concentrations of Saharan Dust will dominate today, and persist through tomorrow afternoon, becoming more moderate through tomorrow night. This will result in hazy skies, reduced visibility and deteriorated air quality.

* Moisture from a tropical wave moving southwest of the region will be displaced early this morning by a drier air mass with high, to locally very high, concentrations of Saharan Dust. This drier air will limit shower activity.

* Breezy ESE winds will result in a moderate risk of rip currents and choppy seas; as winds become lighter marine and beach conditions will improve tomorrow and into the weekend.

* An upper-level low will induce a surface trough that will cross the islands on Saturday, promoting lighter winds as well as a limited flooding and lightning risk.

Short Term(Today through Saturday)

Issued at 322 AM AST Thu Jun 25 2026

Current satellite derived precipitable water (PWAT) values, evidence the moisture field from the tropical wave that has been moving mainly south of Puerto Rico. This wave and associated showers will continue to move westward over the Caribbean Sea early this morning and be displaced by a drier air mass with high, to locally very high, concentrations of Saharan Dust. PWAT values are forecast to decrease to below normal to low-end normal values today and tomorrow as this Saharan Air Layer (SAL) moves over the islands. This SAL will dominate the weather pattern today, and persist through tomorrow afternoon, becoming more moderate through tomorrow night. This will result in hazy skies, reduced visibility and deteriorated air quality. Individuals in sensitive groups (such as those with respiratory conditions, young children, and older adults) should take appropriate precautions and limit prolonged outdoor exposure during this period. This drier air will also serve to limit passing shower activity and afternoon convection. Generally warm 500 mb temperatures will also persist during the period. Under more moderate concentrations, afternoon convection has a better chance tomorrow over mainly interior to W-NW PR.

The surface high pressure over the Central Atlantic will continue to promote breezy E to ESE winds, sharply decreasing tomorrow. An upper-level low is forecast to induce a surface trough that will move across the region on Saturday. This development will weaken the surface high, easing the local pressure gradient and backing winds to a lighter northeasterly flow. Simultaneously, the departure of the SAL will lead to clearer skies and better air quality. PWAT values are expected to be at normal values once again, reaching around 1.80 inches (locally higher). This pattern will favor morning showers across windward sectors, and (with daytime heating and local effects) afternoon showers and isolated t-storms over western to possibly southwestern Puerto Rico (leading to a limited flooding and lightning risk as developing systems will be slow moving). An elevated heat risk will persist during the period, although the drier air today and tomorrow can serve to limit heat indices. 925 mb temperatures are forecast at more normal values today and tomorrow and above normal on Saturday. Highs over urban areas and lower elevations can reach the upper 80s to low 90s while lows will be slightly warmer, especially tonight due to overnight trapping by the SAL.

Long Term(Sunday through Thursday)

Issued at 322 AM AST Thu Jun 25 2026

In the wake of the disturbance, drier conditions are expected at the beginning of the long-term forecast period (Sunday), with below- normal precipitable water values (around or below 1.4 inches). Low concentrations of Saharan dust will begin to arrive, accompanied by a southeasterly wind flow supported by surface high pressure over the eastern Atlantic. The primary hazard during this period will be warm to hot conditions, as forecast guidance indicates 925 mb temperatures around two standard deviations above normal. Daytime highs are expected to reach the upper 80s to low 90s, with heat indices potentially exceeding 100F, particularly across coastal and urban areas. An elevated heat risk is likely to persist throughout much of the forecast period, as 925 mb temperatures are forecast to remain above climatological normals through the week. Residents and visitors are advised to stay hydrated, wear lightweight and loose- fitting clothing, and take frequent breaks in shaded areas if working or spending extended periods outdoors.

From early next week through midweek, current guidance is still suggesting that moisture associated with a tropical wave may approach the Caribbean Basin, increasing low-level moisture across the local islands. Precipitable water values are forecast to rise to near-normal or slightly above-normal levels (around 1.6 to 1.9 inches) based on climatological averages. This increase in moisture would likely enhance rainfall chances, resulting in a greater frequency of showers and afternoon convection. In addition, cooler temperatures aloft associated with lower 500 mb temperatures may provide further support for convective development. However, Saharan dust is also expected to remain present, and its interaction with the incoming moisture introduces some uncertainty to the forecast. Continue to monitor future forecasts for updates as confidence in the evolution of these features improves. By Thursday, drier air is expected to filter into the region, leading to a gradual decrease in rain chances.

AVIATION

(06Z TAFS) Issued at 322 AM AST Thu Jun 25 2026

VFR conditions, although HZ will continue today and reduce visibilities to around 6 SM and promote occasional MVFR conditions, HZ decreasing tomorrow afternoon to night. E to ESE winds increasing after 25/13z to 10-20 kt, with gusts up to 30 kt, and sea breeze variations; winds decreasing after 25/23Z to 5-14 kt, with occasional higher gusts and land breezes.

MARINE

Issued at 322 AM AST Thu Jun 25 2026

A broad high pressure system over the central Atlantic and local effects will maintain moderate to locally fresh easterly winds across the regional waters through the end of the workweek. Choppy marine conditions and Small Craft Exercise Caution conditions will persist across portions of the local waters before gradually improving over the weekend and into early next week as winds diminish. Moderate Saharan dust will continue across the region through Friday, leading to periods of reduced visibility.

BEACH FORECAST

Issued at 322 AM AST Thu Jun 25 2026

A moderate risk of rip currents will continue across most beaches of Puerto Rico and the U.S. Virgin Islands through Friday, decreasing to low from Friday night through Monday before increasing back to moderate by Tuesday as winds strengthen. Beachgoers should remain cautious, as dangerous rip currents can still occur near piers, jetties, reefs, and groins. At least moderate concentrations of Saharan Air Layer (SAL) dust will persist through Friday, producing hazy skies, reduced visibility, and poor air quality, while isolated afternoon showers and thunderstorms may develop each day, mainly across western Puerto Rico.

FIRE WEATHER

Issued at 322 AM AST Thu Jun 25 2026

A Fire Danger Statement has been issued for today across portions of the southern coastal plains of Puerto Rico from 10 AM this morning to 5 PM AST this afternoon due to the combination of critically dry fuels, sustained winds of 15 to 20 mph with gusts up to 30 mph, and minimum relative humidity values in the 40s and low 50s. Moisture from a tropical wave currently moving south of Puerto Rico will continue to be displaced by drier air with high concentrations of Saharan Dust as the day continues. Prolonged rainfall deficits, abnormally dry to drought conditions, and critically dry fuels also continue. These conditions will favor rapid wildfire ignition and extreme fire behavior, meaning any fires that develop will likely spread quickly and become difficult to contain. Outdoor burning is highly discouraged.

SJU WATCHES/WARNINGS/ADVISORIES

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