textproduct: San Juan

KEY MESSAGES

Issued at 302 PM AST Wed Aug 19 2026

- Showers and isolated thunderstorms will continue this afternoon across interior and northwestern Puerto Rico, increasing flooding and lightning threat.

- Warmer conditions are very likely in the next few days, particularly over urban and low-lying areas. Heat Advisories/Warning may be issued if required; stay hydrated.

- A drier airmass along with low to moderate concentrations of Saharan dust will return late tonight into Thursday, persisting through the end of the week.

- The low risk of rip currents continues across all beaches of the islands, becoming moderate Thursday onward.

Short Term(This evening through Friday)

Issued at 302 PM AST Wed Aug 19 2026

A tropical wave (former Invest 94L) moving over the area and an upper trough to our north have provided both above normal moisture and instability over the islands today. Precipitable water (PWAT) values have remained above 2 inches over the islands, with some areas reaching around 2.30 inches, as the tropical waves moisture field continues over the region. Although above normal heat indices were starting to be observed early this morning (as showers and t-storms moved towards windward sectors and surrounding waters), afternoon convection and overall cloudiness has tapered down heat indices in some of the most vulnerable areas. This early mornings above normal diurnal heating, sea breeze convergence, local orographic effects and the above mentioned systems have resulted in strong showers and t-storms over Puerto Rico, particularly over north- central to western and northwestern Puerto Rico. Over these areas, several Special Weather Statements and a Flood Advisory have been issued, small hail has been reported, and up to 2 to around 4 inches have been detected by radar. T-storms also moved over the eastern region, including the metro area, early today.

Through the rest of the afternoon and evening, abundant tropical moisture will continue to be steered towards the islands under ESE winds, prompting additional shower and t-storm development. The moisture field associated with this tropical wave will start exiting the region late tonight, giving way to a drier air mass with low to moderate saharan dust concentrations. PWAT values will sharply decrease to below normal tomorrow, before bouncing back to more normal values on Friday as patches of moisture move over the islands. This drier air mass will also bring low to moderate concentrations of Saharan Dust, with locally high concentrations possible. Although the upper trough should linger north of the area during the period, this drier air mass will leave most available moisture in the low levels. As the surface high also strengthens, breezy flow will also persist tomorrow and Friday and gradually back from ESE to ENE as the workweek continues. Showers over windward sectors are forecast during the morning and night hours while limited afternoon convection is possible tomorrow and Friday (stronger activity) over mainly interior to W-NW PR. While todays weather has provided a relief in terms of heat, high temperatures and heat indices over 100F are still forecast in coastal and urban areas tomorrow and Friday during the late morning to afternoon hours. Because of this an elevated to possibly significant heat risk is expected to return; residents and visitors should take necessary precautions.

Long Term(Saturday through next Tuesday)

Issued at 209 AM AST Wed Aug 19 2026

A generally dry and breezy pattern is expected through the long- term period. Very dry mid-level conditions, warmer-than-normal temperatures aloft, and intermittent Saharan dust should limit the depth and coverage of convection, although patches of low-level moisture and a tropical wave crossing early next week may still support brief passing showers and localized afternoon development. No significant rainfall hazards are anticipated at this time.

Heat will remain the primary hazard, with elevated to locally significant heat risk possible where sufficient sunshine occurs. Persistent breezy winds, dry conditions, and limited wetting rainfall may also continue to support elevated fire weather concerns, particularly across the driest areas. Overall, hazards should remain focused on heat and fire weather rather than rainfall through the period.

AVIATION

(18Z TAFS) Issued at 302 PM AST Wed Aug 19 2026

Although VFR conditions will prevail, brief MVFR conditions are possible mainly over TJBQ and TJSJ through 19/21Z as a tropical wave and a nearby trough continue to promote SHRA/TSRA development. ESE winds up to around 15 kt with sea breeze variations and higher gusts up to 25 kt through 19/23Z and locally higher near strong SHRA/TSRA, winds will gradually decrease overnight, before increasing again after 20/13Z at around 15 kts, with higher gusts and sea breeze variations. HZ will also start to filter over the region from the east from around 20/06Z.

MARINE

Issued at 302 PM AST Wed Aug 19 2026

A surface high pressure building over the Central Atlantic will increase the local pressure gradient and promote moderate to locally fresh winds across the islands. A tropical wave moving across the region will continue to bring showers and isolated thunderstorms, bringing gusty winds and lightning that may become hazardous for small craft. As the tropical wave continues to move across the Caribbean basin, moderate concentrations of Saharan Dust will likely filter into the region late tonight into Thursday, bringing hazy skies and slightly reduced visibility.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...None.