textproduct: San Juan

KEY MESSAGES

Issued at 300 AM AST Mon Jun 22 2026

* Dangerous heat index values will prevail today, especially between 10 AM and 5 PM, as hot temperatures combine with tropical moisture across coastal and urban areas in PR and the USVI. Thus, a Heat Advisory is in effect due to the possible heat-related illnesses without adequate hydration, cooling, and frequent breaks from the heat.

* Moderate concentrations of Saharan dust will filter across the islands once again today, resulting in hazy skies, reduced visibility, and degraded air quality, particularly for sensitive groups. Another pulse of SAL will arrive from Thursday onward.

* A weak tropical wave will move near the region between Wednesday and Thursday, bringing an additional chance for showers and thunderstorms. Forecast details will continue to be refined as confidence increases.

* Life-threatening rip currents will remain possible at exposed beaches through much of the week due to persistent moderate to locally breezy winds. Beachgoers should swim near lifeguards, heed warning flags, and follow local beach safety guidance. St Croix could have a high risk between Wednesday and Thursday due to these increasing winds.

Short Term(Today through Wednesday)

Issued at 300 AM AST Mon Jun 22 2026

Overnight, we had little or no rain as a Saharan Air Layer arrived, creating somewhat dry conditions and hazy skies. As we wrote the discussion, the local mesonet reported temperatures in the low 80s at most coastal sites in the USVI and PR, with some regions along the north coast of PR in the mid or upper 70s. Meanwhile, along the mountains, we observed values from the mid- to upper 60s to the mid-70s Fahrenheit. Most wind stations reported east-to-east-southeast winds around 10 mph or lower, with fluctuations due to land breezes. Meanwhile, some stations in Culebra, St. Thomas, and St. John reported east to east-northeast winds around 15, with higher gusts.

As yesterday's tropical wave moves farther into the central and western Caribbean, a Saharan Air Layer (SAL) will spread across the region, limiting rainfall while contributing to hazy skies, reduced visibility, and degraded air quality. Although dust concentrations are expected to decrease somewhat by Tuesday, traces of suspended dust will likely linger across the local islands. Meanwhile, a mid-level ridge will promote a generally stable pattern with subsidence aloft. At the surface, a strengthening Atlantic high-pressure system will tighten the local pressure gradient, supporting occasional moderate to locally breezy east-to-east-southeast winds. Within this flow, patches of moisture will continue to bring passing showers to windward and eastern areas, while leeward sections experience mostly fair weather. Limited afternoon convection cannot be ruled out, particularly across western Puerto Rico. Seasonably warm conditions will persist, with daytime highs generally reaching the upper 80s to lower 90s across coastal and urban areas, and possible dangerous heat indices each day.

By Wednesday, the leading edge of a tropical wave will bring a modest increase in low-level moisture, with total precipitable water (TPW) values rising to near climatological normals for late June, around 1.65 inches. As moisture increases, the frequency of passing showers is expected to rise across the region, particularly across windward areas. While widespread hazardous weather is not anticipated at this time, isolated thunderstorms and locally heavy downpours cannot be ruled out.

Long Term(Thursday through Monday)

Issued at 300 AM AST Mon Jun 22 2026

Mostly stable weather conditions are expected through the long-term period. While a tropical wave will pass south of the local islands on Thursday, the deepest moisture associated with the system is forecast to remain south of the area. A broad dry air mass will dominate the region, with precipitable water and relative humidity values remaining below normals. As a result, shower activity will be limited to brief trade-wind showers across windward and eastern areas during the overnight and morning hours, followed by isolated afternoon convection over portions of western Puerto Rico. Significant rainfall accumulations and flooding impacts are not anticipated.

Moderate to potentially high concentrations of Saharan dust are expected from Thursday through at least Saturday, promoting hazy skies and periods of reduced visibility. The driest day of the long- term period will be Friday. Individuals with respiratory sensitivities should consider limiting prolonged outdoor activities and following guidance from local health officials.

From Friday through Sunday, fair weather conditions will prevail across most of the region, with only isolated passing showers expected. Temperatures will remain near seasonal levels, while haze and localized reductions in visibility associated with Saharan dust remain the primary weather impacts through the end of the forecast period.

AVIATION

(06Z TAFS) Issued at 300 AM AST Mon Jun 22 2026

A SAL will filter once again across the region, affecting visibilities across portions of the local flying area. Thus, expect HZ with VSBY dropping to near 6 SM, limited SHRA/-SHRA activity, without ruling them out across windward terminals. SHRA will form along the Cordillera and W-PR by 22/16-22z. Winds will be calm to light and variable overnight, and after 22/13z, expect E-ESE winds at 10-20 kt, with gusts up to 30 kt, and sea breezes.

MARINE

Issued at 300 AM AST Mon Jun 22 2026

A broad surface high pressure system over the central Atlantic will maintain moderate to fresh easterly to east-southeasterly winds through the next several days, resulting in choppy seas across most of the local waters. Therefore, small craft should exercise caution. In addition, moderate to occasionally high concentrations of Saharan dust will persist into later tonight, producing hazy skies, reduced visibility, and poor air quality.

BEACH FORECAST

Issued at 300 AM AST Mon Jun 22 2026

A moderate risk of rip currents remains in effect for most local beaches, including northern and eastern Puerto Rico, Vieques, Culebra, and portions of the U.S. Virgin Islands, while a low risk persists for the south-central and western coasts of Puerto Rico and the northern U.S. Virgin Islands. Life-threatening rip currents remain possible.

Meanwhile, moderate to high concentrations of Saharan dust will persist across the region through later tonight, resulting in hazy skies, reduced visibility, and poor air quality.

FIRE WEATHER

Issued at 300 AM AST Mon Jun 22 2026

A Fire Danger Statement has been issued for today across portions of the coastal plains and hills of southern and western Puerto Rico, Vieques and St. Croix 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 low 50s or even in the 40s. 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...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for PRZ001>005-007-008-010>013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for VIZ001-002.

AM...None.