textproduct: San Juan

KEY MESSAGES

Issued at 210 AM AST Mon Aug 10 2026

* Heat remains the main hazard, with elevated to significant heat risks through much of the week.

* Elevated fire danger is expected today as dry, warm, dusty conditions combine with stressed fuels and gusty afternoon winds.

* Tuesday will be the most active weather day, with the highest lightning and localized flooding risk.

* Marine and coastal conditions deteriorate late week as stronger trades build seas and increase the rip current risk.

* NHC is monitoring multiple Atlantic disturbances; it remains too early to determine any impacts to Puerto Rico or the U.S. Virgin Islands.

Short Term(Today through Wednesday)

Issued at 210 AM AST Mon Aug 10 2026

A departing tropical wave will be followed by a drier air mass and increasing Saharan dust today. Lingering moisture and local effects may still support a few afternoon showers and an isolated thunderstorm across interior and western Puerto Rico, but warming temperatures aloft, weak lapse rates, subsidence, and increasing mid-level dryness should keep most of the region dry. An elevated heat risk is expected, and a Heat Advisory has been issued for coastal, lower-elevation, urban, and other heat-prone areas. Some locations could reach significant heat risk levels later today. Saharan dust concentrations will remain high before gradually decreasing overnight.

A surge of tropical moisture will increase shower and thunderstorm activity Tuesday, with the greatest coverage expected during the afternoon. Tuesday carries the highest potential for lightning and locally heavy rainfall, with localized urban and small-stream flooding possible where stronger thunderstorms develop. Pockets of drier Saharan air will gradually follow Tuesday night, before a brief moisture pulse arrives early Wednesday. Cooler temperatures aloft associated with an approaching upper-level trough will favor some convection Wednesday, but increasing mid-level dryness should gradually limit its coverage. Elevated to significant heat risks will continue Tuesday and Wednesday, with the highest heat potential expected Wednesday as warmer low-level temperatures, sufficient humidity, and greater sunshine favor higher heat indices. Winds will decrease today into Tuesday, then begin increasing Wednesday night as the local pressure gradient tightens behind the tropical wave.

Long Term(Thursday through Monday)

Issued at 210 AM AST Mon Aug 10 2026

A tightening pressure gradient associated with the Atlantic ridge will support breezy easterly to southeasterly winds Thursday into the weekend. A drier air mass and Saharan dust will dominate, with precipitable water values dropping to around 1.3 inches Thursday and only brief patches of low-level moisture thereafter. Shower activity should remain limited, with mainly passing showers and very localized afternoon convection. Fewer clouds, warm low-level temperatures, and sufficient low-level humidity will maintain an elevated to significant heat risk, especially across coastal and urban areas, where heat indices could approach 114 degrees. Strengthening trades will also lead to deteriorating marine and coastal conditions late in the week, with building seas and an increasing rip current risk.

Forecast confidence decreases late in the period as NHC continues to monitor multiple disturbances across the central and eastern tropical Atlantic. Guidance suggests that one of these systems could approach the northeastern Caribbean early next week, but considerable uncertainty remains regarding its track, strength, timing, and any potential local impacts. Therefore, the forecast for Monday and beyond may change depending on how these systems evolve.

AVIATION

(06Z TAFS) Issued at 210 AM AST Mon Aug 10 2026

Mainly VFR conditions expected across all terminals during the next 24 hours. HZ will persist, with VSBY occasionally around 6SM. SHRA expected at TJSJ/TIST/TISX after 10/23Z. VCTS possible at TJBQ during the afternoon. SFC winds 8-10 kt early, increasing to 15-20 kt after 10/13Z and continuing through around 10/23Z.

MARINE

Issued at 210 AM AST Mon Aug 10 2026

The Atlantic ridge will maintain moderate to locally fresh easterly winds today, with choppy seas occasionally reaching around 6 feet. Winds and seas should ease somewhat Tuesday as the pressure gradient relaxes. A tropical wave crossing the eastern Caribbean Tuesday into Wednesday will increase the potential for showers and thunderstorms over the local waters. Winds will begin increasing again Wednesday night as the pressure gradient tightens behind the wave, with increasingly hazardous conditions for small craft expected Thursday into Friday. Easterly winds could reach 20 to 25 knots, with seas building to around 6 to 9 feet late in the workweek.

BEACH FORECAST

Issued at 210 AM AST Mon Aug 10 2026

A moderate risk of rip currents will continue today along the northern, eastern, and southeastern beaches of Puerto Rico, as well as Vieques, Culebra, and St. Croix. The risk should gradually decrease, with low-risk conditions becoming more widespread Tuesday night into Wednesday. Even under a low risk, life- threatening rip currents remain possible near groins, jetties, reefs, and piers.

The rip current risk is expected to increase again to moderate across more beaches Thursday as easterly winds and seas increase, with a high risk possible Friday into the weekend. Heat will remain an important beach hazard through the period, while Tuesday will have the greatest potential for dangerous cloud-to-water lightning as shower and thunderstorm activity increases. Saharan dust and haze will persist in pulses through the period.

FIRE WEATHER

Issued at 210 AM AST Mon Aug 10 2026

Elevated fire danger is expected today as very dry and stressed fuels combine with a warmer and drier air mass moving into Puerto Rico behind the departing tropical wave. Saharan air, limited cloud cover, and little to no rainfall will favor additional drying of fine fuels, while afternoon sea-breeze enhancement will support winds of 15 to 20 mph with locally higher gusts, increasing the potential for rapid fire spread where ignitions occur. Refer to the Fire Danger Statement for additional details.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon for PRZ001>005-007-008-010>013. Fire Danger Statement from 10 AM this morning to 4 PM AST this afternoon for PRZ014>016-018-019-024-027.

VI...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon for VIZ001-002.

AM...None.