textproduct: San Juan

KEY MESSAGES

Issued at 200 AM AST Fri Jul 10 2026

* Above-normal temperatures will continue, with the greatest heat impacts expected early next week.

* Elevated to critical fire weather concerns will continue today through the weekend.

* Breezy to windy conditions will persist through early next week.

* Moderate to locally high concentrations of Saharan dust will peak today before gradually diminishing through the weekend.

* The greatest potential for showers and isolated thunderstorms is expected early next week as the next tropical wave moves across the region.

Short Term(Today through Sunday)

Issued at 200 AM AST Fri Jul 10 2026

The primary weather concerns through the short-term period will be breezy to windy conditions, hazy skies, above-normal temperatures, and fire weather concerns. A strong Atlantic surface ridge will maintain brisk easterly trade winds, transporting a drier-than- normal air mass and moderate to locally high concentrations of Saharan dust across the region through Sunday morning. Precipitable water values will remain below normal, while warming mid-level temperatures, dry air aloft, and a persistent trade-wind cap maintain a stable atmosphere. Any available moisture will remain largely confined below 850 mb, limiting vertical cloud development and shower activity to isolated passing trade-wind showers.

By Sunday afternoon and evening, moisture associated with the next tropical wave will gradually increase across the region, allowing precipitable water values to recover to near-normal levels. Meanwhile, an upper-level trough will gradually evolve into a cutoff low while approaching from the northeast. Although these features may support a slight increase in shower activity, organized convection is not anticipated, keeping the flooding and lightning threats low.

Localized areas of heat may affect sensitive individuals, particularly across urban, coastal, and lower-elevation areas. In addition, the combination of gusty winds, low humidity, and increasingly dry fuels will continue to support elevated fire weather conditions, especially across southern Puerto Rico. Refer to the Fire Weather Discussion below for additional details.

Long Term(Monday through Friday)

Issued at 200 AM AST Fri Jul 10 2026

As mentioned in previous discussions a tropical wave is forecast to approach the islands from the east bringing a moister weather pattern by the beginning of the workweek. The latest model guidance continues to suggest mid level relative humidity values ranging between 50 and 75th percentile or near to above normal values for this time of the year. At the same time, the proximity of an upper- level low northeast of the forecast area will maintain slightly cooler mid-level temperatures, around -8 to -9 degrees Celsius at 500 mb, supporting modest instability. With only low concentrations of Saharan dust expected through much of Monday, scattered showers and isolated thunderstorms will be possible. The greatest coverage is expected across the U.S. Virgin Islands and eastern Puerto Rico during the morning, followed by the interior and western sections of Puerto Rico during the afternoon. Locally heavy rainfall may result in ponding of water on roads and in poorly drained areas, with isolated instances of minor flooding.

Saharan dust model guidance suggests that moderate Saharan dust concentrations will approach the islands on Tuesday resulting in hazy skies, periods of reduced visibility, and deteriorating air quality, particularly for sensitive groups. At the same time, the tropical wave will move west of the region while a drier and more stable air mass gradually filters into the area. Precipitable water values are forecast to decrease to near or slightly below normal levels by midweek, while mid-level temperatures gradually warm and relative humidity decreases through the column. As a result, shower activity should become more limited from Tuesday through Friday, with brief passing trade-wind showers during the overnight and morning hours followed by isolated afternoon convection, primarily over the western interior of Puerto Rico. Although localized ponding cannot be ruled out, the overall flooding threat should remain low during the second half of the workweek.

Seasonal to slightly above-normal temperatures are expected through Friday. Combined with sufficient low-level moisture, heat indices will likely exceed 100 degrees Fahrenheit across urban and coastal areas each afternoon, particularly along the northern and southern coastal plains of Puerto Rico and portions of the U.S. Virgin Islands. In addition, the presence of Saharan dust may limit overnight radiational cooling, leading to warmer-than-normal minimum temperatures. Therefore, the heat risk is expected to remain elevated throughout much of the workweek despite the gradual drying trend.

AVIATION

(06Z TAFS) Issued at 200 AM AST Fri Jul 10 2026

VFR conditions will prevail at all TAF sites. HZ will persist due to moderate to locally high concentrations of Saharan dust. E-ESE winds at 8-14 kt will increase to 18-22 kt with gusts around 30 kt between 10/12Z and 10/22Z, diminishing thereafter.

MARINE

Issued at 200 AM AST Fri Jul 10 2026

A broad surface high pressure centered over the Atlantic will continue to support moderate to fresh easterly winds, occasionally strong, across the regional waters through at least late tonight. These conditions will maintain choppy to hazardous seas, with wave heights generally ranging from 5 to 7 feet across the offshore Atlantic waters, Caribbean waters, and the Mona Passage. Small Craft Advisories remain in effect for these waters through at least midnight tonight. Meanwhile, a drier air mass combined with moderate to high concentrations of Saharan dust will persist through the weekend, promoting hazy skies and periods of reduced visibility across the region.

BEACH FORECAST

Issued at 200 AM AST Fri Jul 10 2026

Short period wind-driven waves and breezy conditions will promote a moderate risk of rip currents across most beaches of Puerto Rico and the U.S. Virgin Islands through next week. A moderate risk means that life-threatening rip currents are possible in the surf zone. Beachgoers are urged to exercise caution each day, particularly from the mid-morning hours through sunset.

Additional beach hazards include the presence of Saharan dust, which will continue to cause hazy skies, reduced air quality, and warm to hot conditions during the peak afternoon hours. Sensitive groups should consider limiting prolonged outdoor exposure due to reduced air quality associated with Saharan dust, while everyone should stay hydrated and use caution if spending time under the sun.

FIRE WEATHER

Issued at 200 AM AST Fri Jul 10 2026

Persistent rainfall deficits, critically dry fuels, and elevated KBDI values continue across much of Puerto Rico and the U.S. Virgin Islands, with the greatest concerns across southern Puerto Rico, Vieques, Culebra, and St. Croix. A drier-than-normal air mass, moderate to locally high concentrations of Saharan dust, and breezy to windy easterly trade winds will continue to support favorable conditions for wildfire growth and spread through the weekend. Fire weather concerns will remain elevated to locally critical as low humidity and gusty winds persist. A Fire Danger Statement has been issued today, and additional fire weather products may be needed through the weekend.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Fire Danger Statement from 10 AM this morning to 4 PM AST this afternoon for PRZ014>016-018-019-022-024-027.

VI...None.

AM...Small Craft Advisory until midnight AST tonight for AMZ711-733- 741.

Small Craft Advisory until 6 AM AST early this morning for AMZ712-735.