textproduct: San Juan

KEY MESSAGES

Issued at 249 AM AST Sat Aug 15 2026

- An approaching tropical wave (Invest 92L) will move across the Caribbean Sea, increasing moisture across the area from early this evening into Sunday morning. Therefore, residents can expect an increase in fast-moving showers.

- Heat Risk is elevated today, with a Heat Advisory in effect. Risk may decrease over the weekend, particularly on Sunday, increasing again by early next week.

- Marine and coastal hazards are ongoing and will remain through Sunday. For more detailed information, please refer to the Marine and Beach Forecast sections.

Short Term(Today through Monday)

Issued at 249 AM AST Sat Aug 15 2026

Calm conditions prevailed overnight with a few passing showers moving through the local Atlantic and Caribbean waters. A few reached the northern coast of Puerto Rico without leaving significant rainfall accumulations. Overnight temperatures remained warm, staying in the upper 70s to low 80s in coastal and urban areas, while dropping into the low-to-mid 70s at higher elevations. Breezy conditions continued overnight under a northeasterly wind flow of 10 to 15 mph.

A strong high-pressure system to the north will maintain a tight pressure gradient today, generating breezy to locally windy easterly flow and pushing drier air into the region. Precipitable water (PWAT) values will fall below seasonal normals to around 1.30 inches, keeping rainfall very limited today.

Today, above-normal warm temperatures and abundant sunshine will elevate heat risks, triggering a Heat Advisory today from 10 AM to 5 PM AST across all coastal and urban areas of Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands. The combination of low humidity, dry soils and vegetation, and strong easterly winds will also create conditions favorable for rapid wildfire spread, especially along Puerto Rico's southern and southwestern coastal plains and adjacent slopes, where a Fire Danger Statement is in effect.

Moisture will begin to increase from this evening into Sunday as Invest 92L moves across the Caribbean Sea, passing south of the local islands. Current model guidance suggests the bulk of this tropical wave will stay well to the south, though PWAT values are expected to surge up to 2.10 inches. This surge will bring overnight and early morning showers to the U.S. Virgin Islands and eastern Puerto Rico, followed by scattered afternoon showers and thunderstorms across Puerto Rico driven by daytime heating and local effects. While the strongest storms could produce heavy downpours, lightning, and gusty winds, widespread significant rainfall is not anticipated. Following the wave's passage, drier air and stable conditions will return Sunday afternoon and persist through at least midweek.

Long Term(Tuesday through Saturday)

Issued at 249 AM AST Sat Aug 15 2026

A relatively dry and stable weather pattern is expected Tuesday, followed by increasing moisture and instability Wednesday into Thursday as Invest 94L (AL94) approaches the northeastern Caribbean. On Tuesday, PWAT values should remain around 1.3 to 1.5 inches, with relatively dry mid-levels limiting shower and thunderstorm coverage. Moisture will gradually increase Wednesday, with the most significant surge expected Wednesday night into Thursday, when PWAT could rise to around 2 inches or greater. Increasing low- to mid- level moisture, cooler 500 mb temperatures, and steeper mid-level lapse rates should favor increasing showers and thunderstorms, with locally heavy rainfall and urban and small-stream flooding possible.

Considerable uncertainty remains Thursday into Saturday regarding the evolution, track, timing, and moisture distribution associated with AL94. Regardless of development, the disturbance could bring a substantial tropical moisture envelope across or near the local islands. Small changes in its track or evolution could significantly influence rainfall coverage and amounts. Although moisture may fluctuate Friday into Saturday, cooler temperatures aloft and favorable mid-level lapse rates should maintain an unstable environment, supporting periods of showers and thunderstorms where deeper moisture persists. Therefore, the flooding threat will depend largely on the duration and location of the deepest moisture.

The expected rainfall could provide beneficial moisture to areas experiencing dry conditions; however, significant drought relief is not anticipated, as rainfall amounts and coverage will likely vary considerably. Heat will also remain a concern, particularly Tuesday and during periods of sufficient sunshine later in the week. Increasing humidity may maintain elevated heat indices, while greater cloud and shower coverage Thursday onward could provide some relief. Continue to monitor the latest forecasts and updates regarding the evolution of AL94.

AVIATION

(06Z TAFS) Issued at 249 AM AST Sat Aug 15 2026

Mainly VFR conds expected across all TAF sites. HZ from Saharan dust will continue affecting the local islands, resulting in VIS reductions through 15/22Z. An approaching tropical wave will increase the frequency of SHRA/TSRA later this evening, resulting in VCSH at all terminals aft 15/22-23Z. E winds at 10-15 kt through 15/14Z, increasing to 20-25 kt with gusts 30-35 kt through 15/22-23Z.

MARINE

Issued at 249 AM AST Sat Aug 15 2026

A tight pressure gradient will maintain fresh to locally strong easterly winds and choppy to rough seas around 5 to 7 feet, with occasional seas of 8 to 9 feet across the offshore waters and local passages. Small Craft Advisories remain in effect through at least Sunday. Showers and thunderstorms will increase by Saturday afternoon into Sunday as the tropical wave AL92 moves south of the region, affecting Caribbean waters and local passages.

BEACH FORECAST

Issued at 249 AM AST Sat Aug 15 2026

Dangerous conditions for beachgoers are expected to continue this weekend. The latest nearshore buoys continue to report seas between 3 and 5 feet, while scatterometer data shows winds between 15 - 20 kt, isolated areas between 20 - 25 kt. Based on the latest model guidance, building seas between 5 and 7 feet, occasionally higher, may lead to breaking waves between 6 and 7 feet across exposed beaches of the islands. Therefore, the high risk of rip currents continues across most exposed beaches of Puerto Rico, including Vieques and Culebra, and the U.S. Virgin Islands. Beachgoers must pay attentions to the beach conditions prior entering the waters, as life-threatening rip currents are likely along the surf zone. They should heed the advice of lifeguards, local beach patrol and the flag warning systems. Conditions should gradually improved by Monday, as weakening winds and subsiding seas should lead to a moderate risk of rip currents.

Besides rip currents, beachgoers should stay weather alert particularly this weekend as tropical wave AL92 approaches the Caribbean Basin. Although the system is forecast to move south of the CWA, showers and thunderstorms associated with it may move near the coastal areas of the islands, bringing gusty winds and lightning. They must seek shelter whenever they hear thunder.

FIRE WEATHER

Issued at 249 AM AST Sat Aug 15 2026

Elevated fire danger is expected today as a very dry airmass remains across the region and strong easterly winds continue today with winds between 15 to 20 mph with gusts around 35 mph. Similar to previous days, these conditions combined with little to no wetting rainfall, ongoing rainfall deficits, stressed vegetation, and dry fuels will maintain conditions favorable for rapid fire spread. Therefore, a Fire Danger Statement will be in effect across all Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands from 10 AM AST this morning through 5 PM AST this afternoon.

The northern periphery of an approaching tropical wave (Invest 92L) will approach the U.S. Virgin Islands and the southern coast of Puerto Rico later this afternoon, slightly increasing the moisture content across the area. Nonetheless, the dry conditions will persist until then.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through late Sunday night for PRZ001>003- 005-007-008-011>013.

Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for PRZ001>005-007-008-010>013.

VI...High Rip Current Risk through late Sunday night for VIZ001-002.

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

AM...Small Craft Advisory until 5 PM AST Sunday for AMZ711-723-733- 741.

Small Craft Advisory until 1 PM AST this afternoon for AMZ712- 716-726-735.