textproduct: San Juan

KEY MESSAGES

Issued at 247 PM AST Mon Aug 24 2026

- Heat remains the primary threat, with warm to hot conditions persisting this week along urban and low-lying areas of the islands. Stay hydrated.

- Frequency of showers and isolated thunderstorms will likely increase late tonight into Tuesday, leading to ponding of water over roadways and poorly drained areas, including minor flooding.

- Moderate to high concentrations of Saharan Dust are expected to increase Tuesday night, peaking on Wednesday, bringing hazy skies, reduced visibility, and poor air quality.

- The low risk of rip currents continues across the islands, becoming moderate by the second part of the workweek.

Short Term(This evening through Wednesday)

Issued at 247 PM AST Mon Aug 24 2026

Earlier today, passing showers were observed across the windward areas of Puerto Rico. Around midday, a streamer developed, leaving around 1 to 1.5 inches of rainfall based on radar estimates, particularly across Bayamon and Guaynabo. Showers and thunderstorms then developed across the interior and western portions of Puerto Rico. A Special Weather Statement was issued due to wind gusts of up to 40 mph and frequent lightning. A few Flood Advisories were also issued. Daytime maximum temperatures ranged from the upper 80s to low 90s across coastal and urban areas, and from the low 80s across higher-elevation areas.

The forecast remains on track for another tropical wave to move over the region on Tuesday, which is forecast to be the day with greater rain chances of the short-term period. Precipitable Water values (PWAT) will increase to around the 75th percentile, near 2 inches or higher, along with an increase in 850 to 500 mb relative humidity. Expect the frequency of showers to increase tomorrow morning across eastern areas of Puerto Rico and the U.S. Virgin Islands, followed by the formation of streamers from El Yunque into the metropolitan area and afternoon convection over interior and western Puerto Rico, which could lead to flooding in urban, low-lying, and poor drainage areas. Although an increase in rainfall activity is expected, forecast rainfall accumulations will likely not be enough to significantly improve the ongoing drought conditions across the affected areas.

By late Tuesday night into Wednesday, moderate to high concentrations of Saharan dust particles are forecast to filter into the region. A surface high pressure over the central to eastern Atlantic will slightly shift more to the east, causing winds to shift back to a more easterly direction across the region. Overall, expect hazy skies and a seasonal weather pattern across the islands, with afternoon convection mainly driven by local and sea-breeze effects. A weak upper-level low will linger near the region, leading to cooler 500-mb temperatures that will likely favor the development of thunderstorms.

Additionally, a persistent threat for the remainder of the short- term period will be an elevated to significant heat threat. The issuance of heat product alerts will likely be needed in the coming days. Residents and visitors are encouraged to remain hydrated to help limit the effects of the heat.

Long Term(Thursday through Monday)

Issued at 320 AM AST Mon Aug 24 2026

A surface high pressure system over the central Atlantic will dominate local weather conditions through much of the period, driving mostly east-southeasterly winds across the northeastern Caribbean. A mid-level ridge aloft will further reinforce dry, stable air.

Drier-than-normal conditions are expected to prevail Thursday and Friday, with precipitable water (PWAT) values remaining below the climatological normal of 1.25 inches. Nevertheless, passing patches of moisture will bring brief, fast-moving showers to the region. Afternoon convection driven by daytime heating and localized effects may trigger showers and a few isolated thunderstorms over western Puerto Rico.

From Friday night into Saturday, the latest model guidance suggests a tropical wave will approach the area. However, the bulk of its moisture is expected to remain over the Caribbean Sea, with only the northern periphery reaching the region to bring PWAT values up to 1.751.90 inches. Because some uncertainty remains, residents and local interests should continue monitoring forecast updates as this wave evolves.

PWAT values will drop rapidly following the wave's passage, re- establishing dry, stable air and limiting rainfall chances through early next week. Meanwhile, warmer-than-normal temperatures will persist throughout the forecast period. Model guidance shows 925 mb temperatures running nearly two standard deviations above average for this time of year. Combined with southeasterly winds, seasonal moisture, and Saharan dust, these conditions may warrant heat advisories or warnings by the end of the week.

AVIATION

(18Z TAFS) Issued at 247 PM AST Mon Aug 24 2026

Mainly VFR conds expected across all terminals thru the forecast period. SHRA/TSRA development over W PR may result in intermittent MVFR conds at/near TJBQ betw 24/19Z-23Z. E-ESE winds 10-15 kts with some periods of higher gusts, becoming lighter overnight, increasing again aft 24/13Z. The frequency of VCTS/TSRA/SHRA may increase Tuesday as a tropical wave moves across the region.

MARINE

Issued at 247 PM AST Mon Aug 24 2026

A surface high pressure over the western Atlantic is expected to build and extend into the central Atlantic, promoting moderate east- southeasterly winds across the area, becoming moderate to locally fresh from time to time. Under this pattern, seas will generally remain between 3 and 4 feet, occasionally 5 feet, across the regional waters for the next few days. A tropical wave is forecast to approach the eastern Caribbean on Tuesday, bringing enhanced shower and thunderstorm activity across the local waters and passages. Saharan dust concentrations should gradually increase on Tuesday night, peaking on Wednesday, bringing hazy skies and slightly reduced visibility. A weak long-period swell should arrive and spread across the regional waters by Thursday.

BEACH FORECAST

Issued at 247 PM AST Mon Aug 24 2026

The beach forecast remains on track, as the low risk of rip currents continues across the islands. The latest nearshore buoys continue to report seas between 2 and 3 feet, while winds remain between 15 and 20 kts, with gusts up to 25 kts. Therefore, the risk will remain low for the rest of today, though beachgoers should always pay attention to the beach conditions, as life-threatening rip currents can often occur near groins, jetties, piers, and reefs. These conditions should continue through midweek, becoming moderate for the second part of the workweek and upcoming weekend. A weak long-period swell may arrive and spread across the regional waters by Thursday; breaking waves should remain between 3 and 5 feet, but the risk should remain moderate. Aside from rip currents, residents and visitors should remain weather alert as tropical waves moving across the CWA will enhance shower and thunderstorm activity near coastal areas of the islands. Isolated thunderstorms could produce gusty winds and lightning, and beachgoers should seek shelter whenever they hear thunder.

FIRE WEATHER

Issued at 247 PM AST Mon Aug 24 2026

Around mid-morning, surface stations showed minimum RH values near 55% in Guanica, but values overall remained in the upper 60s or higher across most areas of southern Puerto Rico and the U.S. Virgin Islands. Available moisture across the region from a departing weak tropical wave and local effects are resulting in afternoon showers, which are keeping RH values above critical thresholds through the remainder of the afternoon. As a result, the fire weather risk remains low for the rest of today.

In terms of surface winds, a more east-southeasterly wind pattern is forecast to continue. The arrival of a tropical wave tomorrow, Tuesday, will reduce the fire weather risk and keep it low. However, stressed vegetation and dry fuels are still present, particularly across the southern plains and hills of Puerto Rico and the U.S. Virgin Islands. Residents and visitors are urged to avoid outdoor burning, as conditions could easily support wildfire ignition and rapid spread.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory until 4 PM AST this afternoon for PRZ001>003-005- 007-008-010>013.

VI...Heat Advisory until 4 PM AST this afternoon for VIZ001-002.

AM...None.