textproduct: San Juan

KEY MESSAGES

Issued at 329 AM AST Fri Jun 26 2026

* High concentrations of Saharan Dust will persist through late this afternoon over the region, becoming moderate tonight and low early tomorrow.

* Hazy skies, reduced visibility, limited afternoon convection and deteriorated air quality will continue today.

* Breezy ENE winds will result in a moderate rip current risk and locally choppy seas; as winds become lighter marine and beach conditions will improve tonight and into the weekend.

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

Short Term(Today through Sunday)

Issued at 329 AM AST Fri Jun 26 2026

A Saharan Air Layer (SAL) is moving over the region and will continue to dominate today's weather pattern. These Saharan Dust particulates 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 today. Generally warm 500 mb temperatures will also persist throughout most of the period. Precipitable water (PWAT) values today will be below normal to low-end normal values. The prevailing dry air mass will generally suppress shower development, though local effects could trigger a few afternoon showers across the interior and western and southwestern portions of Puerto Rico as up to breezy steering flow backs today to become more E to ENE. Widespread rain is not expected today. High concentrations of Saharan Dust will persist through late this afternoon over the region, with conditions gradually improving over the USVI first and then gradually over PR as the SAL continues moving westward, generally moderate concentrations are expected tonight. By Saturday, air quality will have improved as the SAL is forecast to have already exited the area. An upper- level low is forecast to induce a surface trough that will move across the region on Saturday. As this surface trough nears the northeastern Caribbean, PWAT values will return to more normal values and reach around 1.8 inches (locally higher). This shift in the pattern will bring morning showers to eastern and windward regions, followed by afternoon showers and isolated thunderstorms over interior to W and NW Puerto Rico as winds veer with the passage of the surface trough and become more E to ESE. Lines of showers can also develop from the USVI and El Yunque. Due to lighter steering winds, these slower moving showers can lead to a limited flooding and lightning risk. Drier conditions will return Sunday following the disturbance, with precipitable water values forecast at below normal values. High pressure over the eastern Atlantic will promote a breezy E to ESE flow, also steering low concentrations of Saharan dust towards the islands. Windward showers and afternoon convection over interior to W-NW PR continue to be forecast. PWAT values will then start to climb late Sunday night as the moisture field from a tropical wave approaches. An elevated heat risk will persist during the period, although the drier air today and Sunday can serve to limit heat indices. 925 mb temperatures are forecast at normal values today and above normal on Saturday and Sunday.

Long Term(Monday through Friday)

Issued at 329 AM AST Fri Jun 26 2026

During the long-term period, a surface high pressure over the eastern Atlantic will maintain a southeasterly low-level flow across the region through the workweek. By Monday into Tuesday, current guidance continues to suggest that moisture associated with a tropical wave will approach the Caribbean Basin, resulting in a gradual increase in deep-layer moisture across the local islands. As a result, precipitable water (PWAT) values should increase to near- normal or slightly above-normal levels, ranging from around 1.7 to nearly 2.0 inches based on climatological averages. In addition, relative humidity within the 700-500 mb layer is forecast to rise to near or above seasonal values. This increase in moisture should enhance rainfall potential, resulting in greater coverage of showers and afternoon convection, with localized ponding of water possible on roads and in poorly drained areas. Cooler temperatures aloft associated with lower 500 mb temperatures may also provide additional support for convective development during the afternoon hours. However, lingering low to moderate concentrations of Saharan dust may limit convective coverage to some extent, introducing uncertainty in the overall coverage and intensity of rainfall. Also, low to slightly moderate concentrations of Saharan Dust is expected to remain present, and its interaction with the incoming moisture introduces some uncertainty to the forecast. By mid week into the end of the week; particularly Thursday and Friday, drier air is expected to filter into the region (PWAT below 1.5 inches), leading to a gradual decrease in rain chances.

One of the primary weather concerns throughout the period will be the persistence of warm to hot conditions. Forecast guidance indicates 925 mb temperatures around two standard deviations above normal, particularly on Monday, when the combination of above-normal temperatures and increasing moisture will promote hot and muggy conditions. Daytime high temperatures are expected to reach the upper 80s to lower 90s, with heat index values potentially exceeding 100 degrees F, especially across coastal and urban areas. As a result, an elevated heat risk is likely to persist through much of the forecast period. Residents and visitors are encouraged to stay hydrated, wear lightweight and loose-fitting clothing, and take frequent breaks in shaded or air-conditioned areas if spending extended periods outdoors.

AVIATION

(06Z TAFS) Issued at 329 AM AST Fri Jun 26 2026

Mainly VFR conditions, although HZ will continue today, reduce visibilities to around 6 SM and promote occasional MVFR conditions. HZ decreasing this evening to tonight. Passing -SHRA/VCSH across windward sectors at times. E to ENE winds increasing after 25/14z to 10-20 kt, with higher gusts and sea breeze variations; winds decreasing after 26/23Z to 5-12 kt, with occasional higher gusts and land breezes.

MARINE

Issued at 329 AM AST Fri Jun 26 2026

A broad surface high pressure system over the Atlantic will maintain moderate to locally fresh easterly winds across the regional waters today. Thus, choppy seas and Small Craft Exercise Caution conditions will persist across portions of the local waters today, before gradually improving over the weekend and into early next week as winds diminish and become more east-southeast. A surface trough is expected to increase shower activity and the potential for isolated thunderstorms across the regional waters around Saturday. Moderate concentrations of Saharan dust will continue through this evening.

BEACH FORECAST

Issued at 329 AM AST Fri Jun 26 2026

Moderate easterly winds will continue to support a moderate risk of life-threatening rip currents along many beaches of Puerto Rico, Culebra, Vieques, and St. Croix today. A moderate risk will persist for the beaches of St. Croix and Culebra on Saturday, and for northwestern Puerto Rico as well on Sunday. Elsewhere, the rip current risk will gradually diminish to low as winds weaken across the region. However, even when the risk is low, isolated life- threatening rip currents can still occur, especially near jetties, groins, reefs, and piers. Beachgoers should swim near lifeguards whenever possible, heed beach warning flags, and follow the advice of local beach patrols.

FIRE WEATHER

Issued at 329 AM AST Fri Jun 26 2026

A Fire Danger Statement has been issued for today (from 10 AM to 4 PM AST) across portions of the southern coastal plains of Puerto Rico due to the combination of critically dry fuels, high KBDI values, sustained winds of 15 to 20 mph with gusts up to 30 mph, and possible minimum relative humidity values in the 40s to low 50s as dry air with high concentrations of Saharan Dust continue moving over the region. Prolonged rainfall deficits, abnormally dry to severe 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. With more E-NE steering flow, shallow afternoon convection could provide some relief to the SW coastal plains today.

SJU WATCHES/WARNINGS/ADVISORIES

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