textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 125 PM CDT Sun Sep 27 2026

- Hot and humid conditions continue through midweek. Heat indices of 110+ degrees on Tuesday and Wednesday afternoons.

- A wetter pattern is looking more likely Thursday into the weekend, with widespread 60-80% rain chances.

- There is a Marginal to Slight (levels 1 and 2 out of 4) risk of excessive rainfall later this week.

DISCUSSION

Issued at 125 PM CDT Sun Sep 27 2026

September will close out hot and mostly dry as ridging in the mid- upper levels remains dominant over deep South Texas. An isolated shower or thunderstorm along the sea breeze cannot be ruled out each afternoon into Tuesday. For the latter half of the week into the weekend, things get more interesting.

A trough over the desert southwest will ingest tropical moisture from the Pacific as it digs into West Texas early this week, bringing along with it a cold front. Midweek, the front is anticipated to stall over central Texas, which pulling Gulf moisture into the region. PWAT values in the latter half of the week could range from 2.3-2.6", nearing climatological maximum values for early October. Mid-level weakness will provide instability to support an increased chance of showers and thunderstorms across the region. Model guidance has continued to suggest heavy rainfall in Texas in the latter half of this week. However, being over 3 days out from the onset of any expected impacts over deep S TX, there remains uncertainty on the timing and axis of the heaviest rainfall. Latest guidance suggests this axis of rainfall will be heaviest to the north of deep S TX, but the forecast will continue to be monitored.

For deep S TX, widespread showers could come as early as late Wednesday, but more likely Thursday or Friday, with moderate to high PoPs continuing into the weekend. This will hopefully bring very welcome rain we've been missing, but training or heavy showers/storms can lead to flooding in low lying, poor drainage, and urban areas. The Weather Prediction Center has placed the region in a Marginal Risk (level 1 of 4) Wednesday, and a Slight Risk (2 of 4) Thursday of excessive rainfall leading to flash flooding.

Hot temperatures with heat indices in the triple digits are expected to continue into midweek, increasing as moisture builds ahead of the front. SPSs are possible Tuesday and Wednesday, and apparent temperatures above 111 degF are possible for brief periods. Increased cloud cover will limit temperatures, but it will still be warm and humid with highs later this week in the 90s.

Local beaches remain pleasant early this week, but will degrade as the front approaches. An increased risk of life threatening rip currents is likely, and increased wave heights may lead to concerns for minor coastal flooding.

AVIATION

(18Z TAFS) Issued at 1215 PM CDT Sun Sep 27 2026

VFR conditions prevail. East-southeasterly winds this afternoon diminish overnight to light and variable, primarily out of the east. There is a low (less than 30%) chance of MVFR ceilings at HRL around sunrise Monday.

MARINE

Issued at 125 PM CDT Sun Sep 27 2026

Gentle to moderate south-southeasterly flow with slight seas prevail through Tuesday morning. 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. Low rain chances (20% or less) will continue through Monday, increasing Tuesday onwards. Rain chances increase to low-moderate (30%) through Wednesday, further increasing to moderate-high (60-80%) Thursday through the remainder of the period. Under any thunderstorms, expect locally higher winds and seas.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 79 96 80 97 / 0 30 30 20 HARLINGEN 74 99 76 100 / 0 10 20 30 MCALLEN 78 102 80 102 / 0 10 10 20 RIO GRANDE CITY 77 102 78 103 / 0 0 0 10 SOUTH PADRE ISLAND 81 89 82 90 / 0 20 30 20 BAYVIEW/PORT ISABEL 77 94 79 95 / 0 10 20 20

BRO WATCHES/WARNINGS/ADVISORIES

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