textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1058 PM CDT Wed Sep 23 2026

- Low to medium (20-40%) rain chances nearly each day to continue through early next week across Deep South Texas, mainly along the sea breeze.

- Above average temperatures (around 5-10 degrees above normal) to continue through the end of September.

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

- 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 Tuesday evening through Thursday timeframe.

DISCUSSION

Issued at 1058 PM CDT Wed Sep 23 2026

The heat punctuated with near daily chances of isolated to widely scattered showers and thunderstorms along the sea breeze will continue to be the primary weather focus through this week. However, there remain some indications of a potential weather pattern change that will feature things cooling down (slightly) mid to late next week, or as we close out the month of September and open the books to October. It's worth noting that climatologically October is one of our fastest cooling months (where our average temperatures falls quickly from the beginning of the month to the end of the month).

The potential weather pattern change mid to late next week to the cooler side will be driven by the flattening of the persistent heat dome that has plagued the region this summer and a sfc cool front. In addition to the cooler changes, this weather pattern change will be highlighted by a potential notable flip to a wetter pattern mid to late next week. In fact, despite the isolated to widely scattered precipitation chances through this week, our next best, real, and more widespread chance for showers and thunderstorms will come mid to late next week (i.e. in the Tuesday evening through Thursday timeframe). Forecast models and ensembles have been advertising this for the past few days now. This round of showers and thunderstorms to come next week will be associated with the interactions of a nearby cool frontal boundary, Gulf moisture, and a nearby shortwave trough.

Through the forecast period or through next week, we have low- medium (20-40%) chances for rain. Had to lower the PoPs some of this week as the NBM was running too high, given the fact that we still are under the influence of a strong 591-594 dam heat dome that will play the role of offsetting any shower or thunderstorm activity through this week.

Temperature wise, through the remainder of this week through Wednesday of next week, forecast models/ensembles continue to advertise the persistent, strong, and broad 591-594 mb heat dome over the region. This will result in a continuation of hotter than normal temperatures throughout Deep South Texas through next Wednesday. High temperatures through next Wednesday will range between the mid 90s to lower 100s with the hottest temperatures occurring in the Sunday through Tuesday of next week timeframe. Widespread Moderate (Level 2 of 4) to Major (Level 3 of 4) with pockets of Extreme (Level 4 of 4) Heat Risk will be common through next Wednesday before a reprieve from the heat takes place next Thursday. During this time, peak heat indices will mainly range between 100-110F degrees through the forecast period.

As far as precipitation, on a persistent easterly flow pattern, low to medium (20-40%) chances for some much needed rainfall in the form of isolated to widely scattered showers and thunderstorms along the sea breeze is possible across Deep South Texas and the Rio Grande Valley nearly each day through early next week.

Once we get into the mid to latter parts of next week (in the September 30-October 2) timeframe, the pattern appears to break down with a sfc cool front and nearby shortwave trough helping to ignite shower and thunderstorm chances. Again, this appears to be our next best and more widespread chance for some very much needed rainfall across Deep South Texas and the Rio Grande Valley. PoPs are in the low- medium range (30-40%) during this timeframe. We will continue to keep close watch on this potential pattern change to cooler and wetter mid to late next week.

AVIATION

(00Z TAFS) Issued at 525 PM CDT Wed Sep 23 2026

Through 00z Friday.....VFR conditions, by and large, are expected to prevail through the 00z TAF cycle. Isolated to widely scattered showers and thunderstorms along the sea breeze is possible Thursday afternoon/evening. Have Prob30 groups to reflect the potential for sea breeze showers and thunderstorms on Thursday for all of the TAF sites. Any showers or storms that move over a terminal will have the capabilities of briefly reducing flight categories down to MVFR-IFR range. Otherwise, expect for VFR conditions to persist.

East-northeast winds 10-15 kts gusting as high as 20 kts or so this evening will weaken later on with things trending towards light and variable to calm tonight. Winds will pick up once again out of the east-northeast 10-15 kts with gusts as high 20-25 kts on Thursday.

MARINE

Issued at 1058 PM CDT Wed Sep 23 2026

Generally, favorable marine conditions will persist through the middle parts of next week with low to moderate seas (wave heights between 1-3 feet) and winds. There could be some SCEC conditions that develop next Tuesday/Wednesday. There will be near day-to-day chances for showers and thunderstorms through the middle of next week. Coverage looks to be isolated to scattered for the most part. Our next best and more widespread chance for showers and thunderstorms will be in the next Tuesday through Thursday timeframe.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 81 96 81 95 / 20 40 40 40 HARLINGEN 78 99 77 98 / 20 30 40 40 MCALLEN 79 99 79 99 / 0 40 30 40 RIO GRANDE CITY 77 99 77 99 / 10 40 30 40 SOUTH PADRE ISLAND 83 90 83 89 / 30 40 50 30 BAYVIEW/PORT ISABEL 80 95 79 94 / 30 40 40 30

BRO WATCHES/WARNINGS/ADVISORIES

TX...None. GM...None.