National Weather Service Today's Weather Impact Levels

429
FXCA62 TJSJ 041756
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
156 PM AST Mon May 4 2026

...New SHORT TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER...

.KEY MESSAGES...
Updated at 156 PM AST Mon May 4 2026

* Locally induced isolated showers over eastern and northwestern
  Puerto Rico this afternoon.

* An approaching trough Tuesday and Wednesday may support
  localized afternoon showers, with brief heavy rainfall possible.
  Isolated thunderstorms cannot be ruled out, though activity
  will remain limited.

* Warmer-than-normal temperatures will persist across Puerto Rico
  and the U.S. Virgin Islands, with heat indices reaching or
  exceeding 100F across urban and coastal areas.

* Mainly a moderate rip current risk will continue along north and
  east-facing beaches of the islands at times.

&&

.Short Term(This evening through Wednesday)...
Issued at 156 PM AST Mon May 4 2026

Overall, mostly calm weather conditions prevailed today across
Puerto Rico and the U.S. Virgin Islands, with mostly clear to
partly cloudy skies observed through much of the day. Temperatures
along coastal areas remained in the upper 80s to low 90s, while
interior and higher elevations ranged from the upper 70s to mid
80s. Winds were predominantly from the southeast, contributing to
warm and somewhat humid conditions across the islands, which
allowed heat indices to reach 100 degrees Fahrenheit in those
urban areas.

For the rest of today into tonight, we anticipated limited to no
rainfall activity, meaning that tranquil weather conditions are
expected to continue under a relatively stable pattern. Partly
cloudy skies will prevail, with only isolated, brief passing
showers possible across windward areas and surrounding waters.
Overnight temperatures will remain warm, generally in the upper
70s along the coast and upper 60s across higher terrain.

By Tuesday and Wednesday, winds area forecast to slightly increase
and become a bit more dynamic as a polar trough and its associated
frontal boundary approaches the region from the western Atlantic.
Although the boundary is expected to remain north of the area, its
proximity combined with surface high pressure over the central
Atlantic will help maintain a southeasterly wind flow across the
region. Precipitable water values are forecast to increase slightly,
with additional patches of low-level moisture advected into the
area, but mainly over the waters, as persistent mid-level drying
continues to inhibit widespread deep convection.

Temperatures will remain above normal through the short-term period,
supported by a warm airmass advected by southeasterly flow. This
will promote heat indices reaching or slightly exceeding 100 degrees
F, especially across coastal and urban areas, resulting in a limited
heat risk. These conditions will mainly impact heat-sensitive
individuals, particularly those exposed to outdoor conditions
without adequate hydration or effective cooling.

&&

.Long Term(Thursday through Monday)...
Issued at 244 AM AST Mon May 4 2026

A transition toward a drier pattern is expected during the mid to
late week period, particularly from around May 7 through May 10, as
moisture decreases and subsidence strengthens across the region.
This will lead to a noticeable reduction in shower activity and
overall rainfall coverage. Temperatures will gradually rise under
this pattern, supporting a limited heat risk, mainly affecting
sensitive individuals exposed to prolonged outdoor conditions
without adequate hydration or cooling.

Breezy conditions will continue, especially during the first half of
the period, with easterly winds occasionally reaching locally fresh
levels. This will result in a limited non-thunderstorm wind risk,
with gusts around 20 to 25 mph possible at times, particularly
across coastal and windward areas. While impacts remain minor,
unsecured objects may be blown around, and these conditions could
contribute to localized hazard enhancement when combined with drying
conditions.

A secondary concern will be the potential for elevated fire danger.
The combination of reduced rainfall, increasing temperatures, and
breezy winds will promote the drying of fine fuels. In addition,
Keetch-Byram Drought Index (KBDI) values exceeding 600 indicate
increasingly dry soil conditions. These factors suggest that fire
danger may increase across portions of the region, particularly
across southern and windward coastal areas. Conditions will continue
to be monitored for any further increase in fire weather risk.

&&

.AVIATION...
(18Z TAFS)
Issued at 156 PM AST Mon May 4 2026

VFR condt are expected to prevail across all terminals. VCSH
possible over TJSJ, TIST, TISX after 04/18Z. Winds will remain
around 12kts with occasional higher gusts, becoming light and
variable overnight.

&&

.MARINE...
Issued at 156 PM AST Mon May 4 2026

A broad high pressure over the central Atlantic will maintain an
easterly to southeasterly flow over the forecast period. Winds
will remain generally gentle to moderate, around 10 to 15 knots,
with periods of locally fresh winds across the Atlantic waters and
Anegada passage at times. Seas will range between 2 and 4 feet,
occasionally up to 5 to 6 feet due to a combination of local wind
waves and a few pulses of a small, long-period northeasterly swell
spreading across the Atlantic waters. Overall conditions will
remain favorable for small craft, though operators should exercise
caution at times due to wind-driven seas and passing showers that
may produce locally higher winds and seas.


&&

.BEACH FORECAST...
Issued at 156 PM AST Mon May 4 2026

Pulses of small, long-period northeasterly swell will occasionally
promote higher breakers and stronger rip currents. As a result, a
moderate risk of rip currents will continue across the north- and
east-facing beaches of Puerto Rico through much of the workweek.
Across the U.S. Virgin Islands, the risk will be moderate at times
along St. Croix and mainly low along St. Thomas and St. John. By
Friday, conditions are expected to gradually improve, with a low
risk briefly prevailing across most beaches, then a moderate risk
returning by the weekend. For additional information and location-
specific rip current details, visit weather.gov/beach/sju.

&&

.FIRE WEATHER...
Issued at 156 PM AST Mon May 4 2026

A Fire Danger Statement (RFDSJU) was issued early this morning
for today. As anticipated, no rainfall have been seen across the
southern sections of Puerto Rico today and drier air mass over the
region is allowing relative humidity values to drop into critical
fire weather thresholds. As of 1:30 PM AST, the Cabo Rojo and
Guanica RAWS stations have been registering RH values in the low
50s and winds speeds in around 10 to 18 mph, with gust around 20
to 27 mph. KBDI values in Cabo Rojo remain above critical fire
weather thresholds. Additionally, the 7-day percent of normal
rainfall across the southeastern coastal plain, including areas
near Salinas, is below 25%, with some locations even below 5%.
Therefore, conditions remain favorable for the spread of wildfires
along the southern coastal plains of Puerto Rico.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...MMC
LONG TERM...ICP
MARINE/BEACH/FIRE...YZR

NWS SJU Office Area Forecast Discussion