textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 608 AM CDT Sat Sep 26 2026

- Hotter than normal temperatures will continue through Wednesday of next week.

- Widespread moderate (level 2 out of 4) to major (level 3 out of 4) heat risk with pockets of Extreme (Level 4 of 4) Heat Risk to continue across the region through Wednesday of next week.

- Heat spikes are possible Tuesday/Wednesday of next week with dangerous heat indices ranging between 105-115F degrees.

- A welcome weather pattern change to cooler and wetter could take shape at the start of October (sometime mid to late next week).

- Our next best and more widespread chances for rain (due to a cool front and nearby shortwave trough) will come mid to late next week; currently have low-medium chances (30-40%) areawide in the Wednesday through Friday timeframe.

DISCUSSION

Issued at 1049 PM CDT Fri Sep 25 2026

The heat will continue to be the main weather storyline through Wednesday of next week. However, Wednesday through Friday of next week (or as we move into the month of October), the storyline will shift towards the increasing chances for a major weather pattern change towards cooler and wetter conditions, driven by El Nino influences.

We start off the forecast period tonight where most of the diurnally and sea breeze driven rain showers will continue to decrease in coverage across the region giving way to dry, warm, and humid conditions under mostly clear skies.

Saturday through Monday of next week, Deep South Texas and the Rio Grande Valley will remain under the influences of a strong heat ridge, though it will begin weakening. Subsidence from the heat ridge will result in rain-free and hotter than normal temperatures. High temperatures during this time will range between the upper 90s to lower 100s.

Tuesday through Wednesday of next week is when things get interesting regarding our aforementioned pattern shift. Hurricane Polo during this time is expected to make landfall over the Baja Peninsula of California, northern Mexico, and eventually northern Texas. Along with the re-curvature of Hurricane Polo, deep tropical moisture from the Eastern Pacific will stream will begin to stream into the region from the west-southwest. Meanwhile, deep tropical moisture from the Gulf of America will begin to stream into the region from the south, courtesy of a large Bermuda high to the east. The combination of deep tropical moisture streaming in from these two source regions along with the aforementioned heat dome in place (though weakening) could result in a heat spike with high heat indices Tuesday and Wednesday. Increased humidity levels with dewpoints in the mid to upper 70s will result in a return to dangerous peak heat indices ranging between 105-113F degrees Tuesday and Wednesday. This will trigger widespread Major (Level 3 of 4) to Extreme Level 4 of 4) Heat Risk over the region. Special Weather Statements (SPSs) and/or a Heat Advisory may be needed Tuesday and Wednesday.

Additionally, during this time (Tuesday through Wednesday of next week), a southeastward advancing cool front will be traversing across Texas gradually approaching Deep South Texas. Meanwhile, there are indications of a weak shortwave trough and mid-upper energies residing near Deep South Texas and northeast Mexico. The combination of a nearby mid-upper impulses, an approaching cool front, and the influx of deep tropical moisture from both the Gulf of America and the Eastern Equatorial Pacific Ocean will support widespread chances for showers and thunderstorms beginning Wednesday and persisting through then end of next week and possibly longer. This is the potential pattern shift that we've been closely monitoring, and if realized, will bring the breakthrough rains that we've been waiting for so long as well as a notably cooler pattern due to the increase cloud coverage and rains. This potential pattern shift to start October has El Nino written all over it. Again, we will continue to closely monitor forecast trends in the days ahead. Currently, we've have low- medium (30-50%) PoPs Wednesday through Friday areawide. It's too early to get into the exact impacts, but heavy rainfall is possible given the surge of tropical moisture.

AVIATION

(12Z TAFS) Issued at 608 AM CDT Sat Sep 26 2026

VFR will prevail at the aerodromes through the next 24 hours, with light to moderate winds and clear to partly cloudy skies. A TEMPO for convection has been added based on the HRRR model.

MARINE

Issued at 1049 PM CDT Fri Sep 25 2026

Generally, favorable marine conditions will persist through Monday of next week with low to moderate seas (wave heights between 1-3 feet) and winds. Tuesday/Wednesday and points forward, conditions will become more adverse due to the threat for showers and thunderstorms as well as increased seas. SCEC to Small Craft Advisories may be needed in the Tuesday through Thursday timeframe.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 95 79 96 79 / 30 0 10 0 HARLINGEN 98 74 99 74 / 20 0 10 0 MCALLEN 101 78 102 79 / 20 0 0 0 RIO GRANDE CITY 101 77 102 77 / 0 0 0 0 SOUTH PADRE ISLAND 89 82 89 82 / 30 0 10 0 BAYVIEW/PORT ISABEL 93 77 94 77 / 20 0 0 0

BRO WATCHES/WARNINGS/ADVISORIES

None.