textproduct: San Juan

KEY MESSAGES

Issued at 325 AM AST Thu May 21 2026

* Breezy to locally windy conditions will continue across the local islands during the next several days, promoting fast moving showers across portions of Puerto Rico and the U.S. Virgin Islands. Keep in mind, gusty winds may blow around unsecured items.

* Breezy conditions will sustain choppy to rough seas at times, and a moderate rip current risk across most of the local beaches. Small Craft Advisories remain in effect through at least later this afternoon for the offshore Atlantic waters.

* Warm to hot temperatures will persist each day with heat indices remaining between 100 and 105F. This will primarily affect heat- sensitive individuals, especially those outdoors without adequate cooling or hydration.

Short Term(Today through Saturday)

Issued at 325 AM AST Thu May 21 2026

Calm weather conditions prevailed overnight across Puerto Rico and the U.S. Virgin Islands under clear to partly cloudy skies. Doppler radar and satellite imagery observed pockets of fast-moving passing showers across the local Atlantic and Caribbean waters; however, only a few of these showers reached portions of Vieques and eastern Puerto Rico during the early morning hours. Overnight lows ranged from the low to mid-70s across coastal and urban areas, and from the low to mid-60s in the higher elevations. Easterly winds prevailed at 5 to 10 mph, with occasional higher gusts and land breeze variations.

A mid to upper-level trough located over the western Atlantic (near the Bahamas) is expected to continue weakening over the next few days as a mid-level ridge builds across the area. At the lower levels, a surface high pressure system over the central Atlantic will continue to strengthen and tighten the local pressure gradient. This setup will promote fresh to locally strong east-southeasterly winds through at least next week.

During the short-term period, precipitable water (PWAT) content will generally remain at seasonal values between 1.5 and 2.0 inches. However, PWAT values will briefly dip slightly below normal today to around 1.30 inches before increasing again by Friday. Under this pattern, passing showers will continue to move over portions of the U.S. Virgin Islands and eastern Puerto Rico, including Vieques and Culebra with minimal impacts. During the afternoon hours, daytime heating combined with local effects will induce convection across western Puerto Rico, triggering showers and a few isolated thunderstorms. Because breezy conditions will persist, these showers are expected to move quickly, keeping the risk of flooding limited over the next few days.

Warm to hot temperatures will persist daily through early next week. Maximum temperatures are expected to range from the upper 80s to low 90s along coastal areas, and from the low to mid-80s in the higher elevations. Heat indices will rise between 100 and 105 degrees Fahrenheit. Residents and visitors are urged to stay hydrated, seek shade, and monitor local conditions to ensure safety during peak heating hours.

Long Term(Sunday through Thursday)

Issued at 325 AM AST Thu May 21 2026

Small changes were introduced to the long-term forecast, as variable conditions may persist early next week, becoming wetter by the end of the period. The wind pattern will continue from the E-ESE as a surface high pressure building in the western Atlantic, maintaining breezy to windy conditions from Sunday through Tuesday, peaking on Monday. However, the high pressure may migrate eastward and linger over the Central Atlantic, weakening and veering winds from the SE Tuesday onward. Moisture content should remain seasonal, with PWAT values ranging between 1.5 and 1.75 inches on Sunday and Monday, but it should gradually increase as abundant moisture pools into the region. According to the latest model guidance, PWAT values could increase up to 2.0 inches, near the climatological normal, with low and mid-level moisture increasing well above normal and sounding models showing skinny profiles. Due to the proximity of the upper- level trough, mid-level temperatures should briefly cool both Sunday and Monday (around -8 degrees Celsius), gradually warming as a mid- level ridge north of the CWA weakens the trough. Although shower activity is expected each day of the forecast, for Sunday and Monday, fast-moving showers are expected over half of eastern Puerto Rico and the U.S. Virgin Islands, with afternoon convection over interior and western Puerto Rico. Additionally, streamers should develop by midday, moving over portions of Vieques, Culebra, and eastern Puerto Rico, including the San Juan Metropolitan Area. Rainfall accumulations could result in ponding of water over roadways and poorly drained areas, along with minor flooding, with a limited flooding threat. Besides flooding, these areas can experience gusty winds and lightning. As winds shift and moisture content increases, the flood threat may remain limited, but an elevated threat (including urban and small stream flooding) over localized areas cannot be ruled out.

With abundant moisture and seasonal temperatures across the region, heat indices over localized areas (particularly urban and coastal) of the islands may reach and exceed 100 degrees Fahrenheit. Nevertheless, the heat will remain limited, likely to impact those sensitive to heat. Stay hydrated and avoid long sun exposure.

AVIATION

(06Z TAFS) Issued at 325 AM AST Thu May 21 2026

VFR conditions across all TAF sites. Breezy to locally windy, E to ESE winds up to 15-22 ktS after 21/13-14Z, with higher gusts and sea breeze variations, decreasing after 21/23Z. Winds will bring periods of -SHRA/VCSH around windward terminals thru 21/23Z. Aftn SHRA/+SHRA and VCTS, will develop across the interior and NW PR possibly resulting in brief MVFR/IFR conds over TJBQ. Breezy to locally windy E to ESE winds at 15-20 kts with higher gusts and sea breeze variations will continue thru 21/23Z.

MARINE

Issued at 325 AM AST Thu May 21 2026

Moderate to fresh easterly winds will continue across the regional waters through the next several days due to strong high pressure over the Atlantic. Choppy to rough seas will persist at times, especially across the offshore Atlantic waters where Small Craft Advisories remain in effect through at least Thursday afternoon. Isolated afternoon thunderstorms may develop near the western coastal waters of Puerto Rico each day, producing locally higher winds and seas.

BEACH FORECAST

Issued at 325 AM AST Thu May 21 2026

Moderate rip current risk conditions will continue across most local beaches through the next several days due to persistent breezy conditions and ongoing wind-driven seas. The highest risk will remain along north and east-facing beaches of Puerto Rico, Culebra, and the U.S. Virgin Islands. Beachgoers should exercise caution, as life-threatening rip currents remain possible.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...Small Craft Advisory until 6 PM AST this evening for AMZ711.