textproduct: San Juan

KEY MESSAGES

Updated at 235 PM AST Wed Jul 29 2026

- Dangerous heat indices remains. Therefore, an Extreme Heat Warning remains in effect for the urban and coastal areas Puerto Rico until 5 PM AST today. A Heat Advisory remains in effect for the US Virgin Islands through 5 PM today. Additional Heat product may be needed through the remainder of the week.

- Some showers and thunderstorms will continue to develop this afternoon, mainly across northwestern portions of Puerto Rico, producing frequent lightning, strong wind gusts, torrential rainfall, and localized flooding.

- Increasing easterly winds will continue to generate choppy seas through the week, resulting in building seas, potentially small craft advisories and a higher risk of life-threatening rip currents along exposed beaches.

- A drier air mass accompanied by Saharan dust will gradually overspread the region through at least Friday. Expect hazy skies, reduced air quality, and temperatures remaining above normal despite a decrease in overall rainfall coverage.

- Another tropical wave may approach the region late by Sunday into early next week. Although forecast confidence remains low, it could lead to increased showers and thunderstorms.

Short Term(This evening through Friday)

Issued at 235 PM AST Wed Jul 29 2026

Mainly fair weather conditions and hazy skies have prevailed across the forecast area throughout the morning hours, with the exception of a few light passing showers across the eastern half of Puerto Rico. The primary hazard today has been the heat. As mentioned in the previous update, the Heat Advisory for Puerto Rico was upgraded to an Extreme Heat Warning as heat indices exceeding warning criteria became more widespread across coastal and urban areas due to the combination of high temperatures and elevated humidity. Continue to take the necessary precautions, especially if spending prolonged periods outdoors during the peak heating hours.

A record high temperature of 94F was observed today in the San Juan Area at the Luis Munoz Mar?n International Airport climate station. This breaks the previous record of 93F, set in 1984 and 2013. This also marks the second consecutive day that this official climate station has set a new daily maximum temperature record and the eighth consecutive day with a maximum temperature of 90F or higher.

For the remainder of the afternoon, convection driven by daytime heating, sea breeze convergence, and local orographic effects is expected to develop across the west-central to northwestern portions of Puerto Rico. Although activity should remain localized, isolated thunderstorms may produce ponding of water on roads and in poorly drained areas.

As the Atlantic high pressure continues to strengthen, tightening the local pressure gradient, easterly to southeasterly winds have generally ranged between 15 and 20 mph, with occasional gusts of 25 to 30 mph. The breezier days are expected from the rest of today and Thursday. Behind the departing tropical moisture, a drier air mass will overspread the region after 6 PM AST this afternoon and Thursday. The latest model guidance remains consistent in indicating precipitable water values below 1.5 inches, or around the 25th percentile of climatological normal. This drier air mass will be accompanied by low to moderate concentrations of Saharan dust, which are expected to linger through at least early Friday. Nevertheless, available low-level moisture and daytime heating will continue to support localized afternoon showers and isolated thunderstorms, mainly across the northwestern quadrant of Puerto Rico, although coverage should remain limited. On Friday, a weak wind perturbation is expected to move across the region, resulting in a brief increase in passing showers over the windward areas of Puerto Rico and the U.S. Virgin Islands before the typical afternoon convection redevelops across the interior and western portions of Puerto Rico.

For the remainder of the short-term forecast period, warm to hot conditions will persist across coastal and urban areas. Residents and visitors are encouraged to stay hydrated, limit outdoor activities during the hottest part of the day, and continue practicing heat safety measures.

Long Term(Saturday through Wednesday)

Issued at 313 AM AST Wed Jul 29 2026

A variable weather pattern continues for the long-term forecast period. A strong surface high-pressure system located over the central Atlantic will maintain breezy conditions under a southeasterly wind flow through Monday. A tropical wave and an upper- level low are approaching the local area early next week, increasing moisture and instability across the northeastern Caribbean region.

The latest model guidance continues to suggest seasonal precipitable water (PWAT) values between 1.60 and 1.80 inches on Saturday. However, from early Sunday through late Monday, PWAT values will gradually increase as the tropical wave and upper-level low position over the region, bringing above-normal PWAT values of 2.00 to 2.10 inches. As the upper-level low arrives, cool mid-level temperatures (around -6 to -7 degrees Celsius at 500 mb) combined with enhanced lifting will promote cloud growth and atmospheric instability.

During this weather scenario, frequent passing showers are expected across portions of eastern Puerto Rico and the U.S. Virgin Islands, followed by afternoon convective activity across central and western Puerto Rico. Showers and thunderstorms accompanied by frequent lightning are anticipated during this period. Due to current drought conditions, any rainfall will be beneficial for the islands regardless of where it falls. Elevated temperatures will persist throughout the perioddriven by normal to above-normal temperatures at the 925 mb levelwith daytime highs reaching the upper 80s to low 90s across coastal and urban areas.

By Wednesday, another mid-to-upper-level low will approach the region, further increasing instability and moisture. However, uncertainty remains regarding exact impacts. Residents and visitors are encouraged to stay informed and monitor weather updates as the week progresses.

AVIATION

(18Z TAFS) Issued at 235 PM AST Wed Jul 29 2026

Mainly VFR conditions are expected across most TAF sites during this forecast period, except at TJBQ where VCTS/TSRA will remain more probable, likely resulting in intermittent MVFR conditions thru 29/21Z. The presence of low to moderate concentrations of Saharan dust across the region will lead to slight reductions in visibility from this afternoon into the coming days. Another aviation concern will be the winds, with gusts near 30 kt expected today thru 29/23Z and returning 30/13Z through 30/23Z.

MARINE

Issued at 235 PM AST Wed Jul 29 2026

The surface high pressure over the central Atlantic will continue to strengthen, tightening the pressure gradient and promoting moderate to locally fresh east to east-southeast for the next few days. These conditions will maintain periods of choppy seas across portions of the local Atlantic and Caribbean waters, including the local passages. This could potentially generate dangerous conditions for small crafts. Moderate concentrations of Saharan Dust will bring hazy skies and slightly reduce visibility throughout the workweek. An approaching tropical wave is forecast to reach the region late in the weekend.

BEACH FORECAST

Issued at 235 PM AST Wed Jul 29 2026

Expect the moderate risk of rip currents to prevail across exposed beaches of northern and eastern Puerto Rico, including Vieques and Culebra, and the U.S. Virgin Islands. As winds continue to strengthen, the moderate risk will spread across southern Puerto Rico, while the western beaches remain under a low risk. Although the risk is not high, beachgoers should continue to exercise caution as life-threatening rip currents remain possible along the surf zone. The moderate risk should persist throughout the workweek, but it may downgrade along southern beaches of Puerto Rico and St. Thomas and St. John in the U.S. Virgin Islands as winds weaken once again during the weekend. Nevertheless, beachgoers should be aware of life-threatening rip currents in the vicinity of jetties, groins, reefs, and piers. Besides rip currents, beachgoers should stay weather alert as showers and isolated thunderstorms could still be expected in the afternoons.

FIRE WEATHER

Issued at 235 PM AST Wed Jul 29 2026

Relative humidity values remained near or above critical thresholds today with breezy to windy conditions. Critically dry fuels persist across southern Puerto Rico and St. Croix. East- southeasterly winds are forecast to remain breezy to windy through the rest of the workweek, which could promote the spread of any fire that develops. Additionally, a drier airmass accompanied by Saharan dust will spread over the region later this afternoon and tomorrow, leading to more favorable conditions for fire spread. Residents and visitors should avoid outdoor burning and exercise caution with activities that could generate sparks or open flames. Fire weather partners should continue to monitor the forecast, particularly tomorrow, Thursday.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Extreme Heat Warning until 5 PM AST this afternoon for PRZ001>005-007-008-010-011.

Heat Advisory until 5 PM AST this afternoon for PRZ012-013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...None.