textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 212 PM CDT Mon Sep 28 2026

- Hotter than normal temperatures will continue through Thursday.

- Widespread Major (Level 3 out of 4) heat risk with pockets of Extreme (Level 4 of 4) Heat Risk to continue across the region through Thursday.

- Heat spikes are possible Tuesday-Thursday with dangerous heat indices ranging between 105-115F degrees; Special Weather Statements (SPSs) and Heat Advisories may be needed.

- Confidence is increasing on a significant weather pattern change towards markedly cooler and wetter conditions later this week; this includes a multi-day heavy rain and flash flood potential Thursday through early next week.

- Preliminary rainfall amounts of 2-4 inches with locally higher amounts is possible Thursday through Sunday night.

- The Weather Prediction Center (WPC) has all of Deep South Texas under a Slight (Level 2 of 4) Risk for Excessive Rainfall for Thursday, and a Marginal to Slight (1 to 2 of 4) Risk Friday.

- Breezy southeast winds 15-25 mph with gusts up to 35 mph or so will result in SCEC to Small Craft Advisories for the Laguna Madre and the Gulf Tuesday and Wednesday as well as increased rip current risks along the beaches.

DISCUSSION

Issued at 212 PM CDT Mon Sep 28 2026

Hot and humid conditions continue through Thursday as ridging remains in place across deep South Texas. Afternoon heat indices will remain in the triple digits, potentially exceeding 111 degrees for brief periods. Heat Advisories and/or SPSs are possible daily through Thursday. Increasing moisture and cloud cover ahead of an approaching front will limit temperatures later in the week, with highs in the 90s (and will likely end McAllen's record-breaking 100+ degree day streak).

The pattern will become increasingly unsettled late this week into the weekend as troughing over SW US ingests deep tropical moisture from the Pacific. As the trough traverses east, the associated cold front is expected to stall over central TX midweek, while persistent southerly to southeasterly flow transports additional Gulf moisture into the region. PWAT values could reach 2.3-2.6" later this week, near climatological maximum values for early October, supporting efficient rainfall rates in any showers.

As the front slowly moves southeast, rain chances increase late Thursday from west to east, peaking across the CWA Friday (70-90%), and continuing through the weekend with widespread moderate to high PoPs (50-70%). There is still uncertainty in the evolution of this system, as model guidance continues to differ on the timing and placement of heaviest rainfall. At this time, the axis of heaviest rainfall looks to be to our north. The overall signal for a wetter pattern has remained consistent, but the location of heavier rainfall in deep S TX will depend on where slow-moving or training convection develops.

Early estimate rainfall totals for Thursday to Sunday are around 2- 4 inches, with the highest totals expected across western portions of deep S TX. Locally higher amounts cannot be ruled out, and any slow-moving or training showers and thunderstorms could produce locally heavy rainfall. This rainfall will be beneficial given ongoing drought conditions, but runoff and flash flooding could occur, particularly in low-lying, poor drainage, and urban areas. Guidance will continue to be monitored closely as the event approaches and the timing and rainfall axis become better defined.

The Weather Prediction Center has highlighted the region for an increased risk of excessive rainfall, with a Slight Risk Thursday, and a Marginal (coast) to Slight Risk (east of I-69E) Friday.

Local beaches will remain relatively pleasant today and much of tomorrow, but will deteriorate as the front approaches. Increasing wave heights and stronger onshore flow will bring an increased risk of life-threatening rip currents, with minor coastal flooding also possible around high tide Tuesday night through the weekend.

AVIATION

(18Z TAFS) Issued at 1212 PM CDT Mon Sep 28 2026

VFR conditions prevail through the cycle. Few-sct clouds at 050 will continue passing over the Valley through the afternoon, with east-southeast winds at 10-15 kts and a low (10%) chance of an isolated sea breeze shower or thunderstorm. Winds diminish overnight.

MARINE

Issued at 212 PM CDT Mon Sep 28 2026

Gentle to moderate south-southeasterly flow with slight seas prevail through Tuesday. An increasing pressure gradient will degrade conditions by midweek, with Small Craft Advisory conditions possible as early as Tuesday night with seas building to 4-7 ft. Unfavorable marine conditions will continue through Thursday. Low rain chances (20-30%) also continue through Thursday, increasing to moderate-high (60-80%) Thursday night behind the front, persisting through the remainder of the period. Under any thunderstorms, expect locally higher winds and seas.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 80 97 82 98 / 20 20 10 10 HARLINGEN 76 100 80 101 / 10 20 10 10 MCALLEN 80 102 82 103 / 10 10 20 0 RIO GRANDE CITY 78 103 80 104 / 0 0 0 0 SOUTH PADRE ISLAND 82 90 83 90 / 20 20 10 10 BAYVIEW/PORT ISABEL 78 95 80 96 / 10 20 10 10

BRO WATCHES/WARNINGS/ADVISORIES

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