textproduct: San Juan

KEY MESSAGES

Issued at 257 AM AST Tue Nov 3 2026

- Hot and humid conditions will lead to increasing heat indices and with it the risk of heat related illnesses, especially for those spending extended periods outdoors. Therefore, a Heat Advisory will be in effect from 9 AM through 2 PM today.

- Expect afternoon showers and thunderstorms to develop over western and northwestern Puerto Rico. Ponding of water over roads and poorly drained areas remains possible for today.

- Slow-moving showers and thunderstorms Thursday through Saturday may produce urban and small-stream flooding, with isolated flash flooding possible, particularly across northern and interior Puerto Rico.

- Weather conditions will improve from Sunday into early next week, although afternoon showers remain possible.

- Choppy marine conditions will gradually improve through midweek as winds and seas diminish. The risk of rip currents will also decrease across many beaches. However, another swell arriving late in the week could bring hazardous surf and rip current conditions during the weekend, particularly along the northern coast of Puerto Rico and the northern U.S. Virgin Islands. Refer to the Beach Forecast section for additional details.

Short Term(Today through Thursday)

Issued at 257 AM AST Tue Nov 3 2026

Generally calm weather conditions prevailed across Puerto Rico and the US Virgin Islands overnight, with mostly clear skies across Puerto Rico and isolated to scattered showers affecting the surrounding waters and portions of the US Virgin Islands, although rainfall accumulations remained minimal. Temperatures dropped into the 70s along coastal areas of Puerto Rico and into the 60s across higher elevations, while the US Virgin Islands remained in the upper 70s to lower 80s under partly cloudy skies. Winds were generally light.

For today, above-normal temperatures, abundant surface moisture, and a prevailing southerly wind component will favor elevated heat indices across Puerto Rico and the US Virgin Islands for the first half of the day. Following several days of temperatures reaching the lower 90s, mostly clear skies overnight and through the morning hours will allow rapid daytime heating, with heat indices approaching 108 degrees Fahrenheit or briefly higher, particularly across coastal and urban areas. Given these conditions, the first Heat Advisory of November has been issued from 9 AM to 2 PM AST. Increasing cloud cover and afternoon showers and thunderstorms should provide some relief from the heat later in the day. Residents and visitors are urged to stay hydrated, limit strenuous outdoor activities, and seek shade or air-conditioned environments when possible.

Aside from the heat, east-southeasterly winds, combined with daytime heating and local effects, will favor afternoon showers and thunderstorms across the western interior and northwestern portions of Puerto Rico, where the highest rainfall accumulations are anticipated. Although localized ponding of water and lightning will remain possible, widespread flooding is not anticipated today.

Looking ahead through Thursday, the latest model guidance suggests a gradual increase in atmospheric moisture and instability, with precipitable water values reaching 2.0 to 2.3 inches and the greatest potential for convective activity expected late Thursday. As a frontal boundary remains just north of the region, winds will gradually shift to southerly by midweek and west-southwesterly on Thursday, shifting the focus of afternoon convection toward the northern half of Puerto Rico. Additionally, weakening winds may allow showers and thunderstorms to linger over the same locations, increasing rainfall accumulations and lightning threats. By Thursday, deeper moisture and slow-moving convection will increase the potential for urban and small-stream flooding, with a low chance of isolated flash flooding. Saharan dust concentrations are expected to remain low through the end of the workweek.

Long Term(Friday through Tuesday)

Issued at 257 AM AST Tue Nov 3 2026

For Friday through Saturday, atmospheric instability is expected to remain elevated. Precipitable water (PWAT) values will continue above normal (between 2 to 2.3 inches) through at least Sunday. Relative humidity (RH) in the 850700 mb layer will stay high while mid-level moisture (700500 mb) is set to increase to 80% through early Saturday. An upper-level trough, along with its corresponding surface low and frontal boundary, will track northward across the Atlantic. Although the core of maximum instability is expected to pass north of the area, this will set up a southwesterly to westerly (light to variable) steering flow, drawing tropical moisture northward into our area. This steering flow will be generally light and variable. Consequently, slow-moving showers are likely to develop, generating elevated rainfall totals, primarily across the southern, interior, northern and northeastern sectors of Puerto Rico, as well as the U.S. Virgin Islands. This will result in flooding (Risk level 2 of 4) especially across interior, northern and northeastern Puerto Rico during the afternoon hours. Although model guidance continues to indicate mid to upper level ridging building over the islands to start the next week, prompting a more stable pattern. Model discrepancies continue through Tuesday. The GFS preserves higher moisture availability throughout the atmospheric column, specifically within PWAT, 850700 mb RH and 700- 500 mb RH. Conversely, the ECMWF projects a drier 850-500 RH profile alongside reduced PWAT values. Uncertainty continues to be present concerning the overall moisture content. While daytime heating and local effects can trigger isolated to scattered afternoon showers across the islands, an overall reduction in rainfall coverage and intensity is anticipated, thereby lowering the risk of flooding. Steering flow Sunday through Tuesday is forecast to be generally light to variable from the southwest before gradually backing and becoming more southerly as the period continues. Please monitor future updates as changes to the forecast are possible.

AVIATION

(06Z TAFS) Issued at 257 AM AST Tue Nov 3 2026

All TAF sites should experience VFR conditions. However, brief period of MVFR conds possible with SHRA and TS, occasionally reaching TJBQ and TJSJ after 03/17Z. Winds will become SE around 10-15 kts, with stronger gusts near the heaviest thunderstorms activity. Winds will become lighter (3 to 5 knots) by 03/23Z. Expect VCSH over TIST and TISX after 04/00Z.

MARINE

Issued at 257 AM AST Tue Nov 3 2026

A weakening Atlantic ridge will initially maintain light to moderate east to southeast winds. Winds will gradually become southerly as a frontal boundary approaches from the northwest and a weak surface low develops north of Puerto Rico by Thursday. The weakening pressure gradient will favor light, variable winds, with subsequent wind shifts depending on the low's evolution. Seas will generally subside through midweek before a northerly swell arrives Friday into the weekend, building seas across the Atlantic waters and exposed passages.

BEACH FORECAST

Issued at 257 AM AST Tue Nov 3 2026

A moderate risk of rip currents will persist along portions of the north- and east-facing beaches of Puerto Rico and the northern US Virgin Islands through midweek, including portions of St. Croix today. A northerly swell arriving Friday into the weekend will increase surf and maintain a moderate rip current risk along the northern US Virgin Islands and northern Puerto Rico, expanding to western beaches by Saturday. Elsewhere, the risk will generally remain low, although isolated stronger rip currents are still possible near piers, jetties, and channels. Isolated thunderstorms could also pose a lightning threat to beachgoers, particularly across Puerto Rico, Vieques, and Culebra each afternoon. Seek shelter indoors if thunder is heard.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory from 9 AM this morning to 2 PM AST this afternoon for PRZ001>013.

VI...Heat Advisory from 9 AM this morning to 2 PM AST this afternoon for VIZ001-002.

AM...None.