textproduct: San Juan

KEY MESSAGES

Issued at 208 PM AST Tue Jun 9 2026

* Dangerous heat will continue through much of the week. Heat indices may exceed 100F, especially across urban, coastal, and lower-elevation areas of Puerto Rico and the U.S. Virgin Islands. Heat Advisories may be needed at times. * A wetter and more unstable weather pattern is expected on Wednesday and especially Thursday as a tropical wave interacts with an approaching upper-level trough, increasing the coverage of showers and thunderstorms across the region, and posing the greatest risk of flooding for Thursday.

* Traces of Saharan dust will persist through the forecast period, producing somewhat hazy skies and reduced air quality, especially trailing the wave into early Saturday.

* The potential for life-threatening rip currents will turn moderate from Thursday onward, first across St Croix, then spreading to the rest of the east and north-facing beaches in the USVI and PR.

Short Term(This evening through Thursday)

Issued at 208 PM AST Tue Jun 9 2026

Warm and hot weather conditions prevailed today with heat indices between 100 and 110 degrees Fahrenheit in many coastal and urban locations in PR and the USVI. The Doppler radar observed little or no rain this morning. At the time of writing, air temperatures ranged from the upper 80s to the low 90s along PR and the USVI's coastal areas, to the mid- or low-80s in mountain areas. Winds were mainly from the east at 10 to 15 mph, with higher gusts and sea-breeze variations.

Heat indices remain dangerous for vulnerable communities this afternoon; therefore, a Heat Advisory continues for coastal and urban areas in Puerto Rico and the U.S. Virgin Islands. The aforementioned excessive heating, combined with variations in sea breezes and local factors, is expected to lead to showers this afternoon, and we cannot rule out at least a thunderstorm in the interior or western regions of Puerto Rico. However, the presence of dry air and warmer-than-normal temperatures at 500 mb (in the 75th percentile for June) will limit this potential. Once again, later this evening, the weather is expected to be calm, with warmer-than-average overnight temperatures. Some showers may reach the windward areas of Puerto Rico and the U.S. Virgin Islands.

For Wednesday, the subsidence ahead of the Thursday weak tropical wave will promote a somewhat calm weather pattern, featuring warmer-than-normal temperatures, dangerous heat indices, and a few quick-moving showers across windward areas during the morning. However, a polar trough amplifying across the western Caribbean and later near the northeast Caribbean around Wednesday and Thursday, will enhance instability and the potential for thunderstorms. Therefore, although we are expecting calm weather early on Wednesday, afternoon convection will develop across the interior and western PR, as well as downwind from the USVI and El Yunque into the San Juan metro. This pattern will increase the risk of flooding and water ponding on roads and in poorly drained areas, as well as isolated urban flooding.

Although the potential for warm and hot temperatures will persist on Thursday, there is a greater chance of urban and small-stream flooding, along with isolated flash flooding, as the tropical wave interacts with the polar trough swinging across the region. Some of the limiting factors associated with the aforementioned weather pattern include possible cloud cover from the mid- to upper-level trough, which could inhibit afternoon convection and reduce the amount of heating we experience. That said, currently the most wet and unstable weather potential for the short term is Thursday. Therefore, we encourage our residents and visitors to monitor weather conditions, as we will update them as conditions require.

Long Term(Friday through next Monday)

Issued at 110 AM AST Tue Jun 9 2026

No major changes were made to the long-term forecast, as weather conditions are expected to become drier and more stable over the upcoming weekend and early next week. A surface high pressure building over the Western Atlantic should increase the local pressure gradient, leading to strengthening east-southeast winds and resulting in breezy to locally windy conditions across the islands. Friday has the highest potential for flooding and lightning, as lingering moisture associated with a tropical wave and the proximity of an upper-level trough should enhance afternoon convection. From the latest model guidance, PWAT may vary between 1.7 and 1.9 inches, which is typical for this time of the year, but shows abundant low to mid-level moisture. Due to the proximity of the trough, mid-level temperature should remain cooler than normal (500 mb temperatures around -8 degrees Celsius), with enhanced vorticity, rising air, and divergence aloft across the region, favorable for deep convection. Additionally, the Galvez-Davison Index (GDI) suggests the potential of isolated to scattered thunderstorms, particularly over the western/northwestern side of the CWA in the afternoon. Although a drier airmass will gradually filter into the region on Friday, passing showers can still be expected during the morning hours over windward sections of the islands, followed by afternoon convection over interior and western/northwestern Puerto Rico. Additionally, island streamers may develop and bring some showers into eastern portions of Puerto Rico, including the San Juan Metropolitan area. Rainfall accumulations could lead to ponding of water over roadways and poorly drained areas, including minor flooding, over the aforementioned areas. As the drier air mass continues to filter into the region, patches of moisture may arrive throughout Saturday, with shallow afternoon convection over western/northwestern Puerto Rico. Sunday and Mondays forecast remains uncertain, as the latest global model solutions show different outcomes for the CWA. The latest GFS solution showed the upper-level trough lingering near the region, with PWAT values remaining near above normal (up to 1.9 inches), while the ECMWF solution suggests a mid-level ridge near the CWA, with drier air in the 850 - 500 mb layer. Due to inconsistency with the GFS solutions, Sunday and Mondays forecast was based on a similar pattern to Saturday, with limited rainfall activity.

In terms of heat, warmer conditions may persist throughout the forecast period as model guidance suggest typical to above normal 925 mb temperatures. With the available moisture, heat indices above 100 degrees Celsius cannot be ruled out, particularly across urban and lower elevations of the islands. Hence, residents and visitors should exercise caution as these levels could impact most individuals, particularly those without adequate hydration and/or effective cooling.

AVIATION

(18Z TAFS) Issued at 208 PM AST Tue Jun 9 2026

Mainly VFR conds expected at all TAF sites thru the fcst period. Trace Saharan dust will persist, but VIS should remain P6SM for the most part. VCSH/SHRA will continue at times, mainly thru 09/22Z and again aft 10/13Z. VCTS is psbl at TJPS and TJBQ aft 10/17Z. Brief MVFR conds psbl in heavier SHRA/TSRA due to reduced VIS and low cigs. ESE winds 12-15 kt with sea breeze variations and hir gusts thru 09/22Z, bcmg lgt/vrb to lgt E overnight, then incrg aft 10/14Z.

MARINE

Issued at 208 PM AST Tue Jun 9 2026

The Azores high will continue to promote moderate winds tonight and tomorrow. Then, a tropical wave crossing the Lesser Antilles on Wednesday and moving across the local islands while interacting with a deep polar trough on Thursday will enhance the potential for showers and thunderstorms, especially from Wednesday afternoon into late Thursday night. Mariners should prepare for stronger winds and higher seas near thunderstorms.

BEACH FORECAST

Issued at 208 PM AST Tue Jun 9 2026

The rip current risk is low for the rest of today and tomorrow. However, life-threatening rip currents may still occur, especially near groins, jetties, reefs, and piers.

From Thursday onward, life-threatening rip currents are possible, first across St Croix, then spreading to the rest of the east and north-facing beaches in the USVI and PR. Always swim near a lifeguard and remember to heed the advice of the local beach patrol and flag warning systems.

FIRE WEATHER

Issued at 110 AM AST Tue Jun 9 2026

Drier-than-normal conditions will enhance the availability of burning fuels along the southern plains of PR and the USVI. The fire danger fro today is low, as conditions are present.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007- 008-010>013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...None.