textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 559 AM CDT Thu Oct 1 2026

- Widespread Major (level 3 of 4) to Extreme (level 4 of 4) Heat Risk expected across the region Thursday.

- Cooler and wetter conditions are expected Thursday afternoon into early next week due to a frontal passage and a multi-day rainfall event.

- The Weather Prediction Center (WPC) has Deep South Texas under a Slight (level 2 of 4) to Moderate (level 3 of 4) Risk for flooding rainfall for Thursday, a Marginal (level 1 of 4) to Slight Risk on Friday, and a Marginal Risk along the coast on Saturday.

DISCUSSION

Issued at 1111 PM CDT Wed Sep 30 2026

Heat will continue to be a concern Thursday afternoon, with high temperatures forecast to range from the upper 90s to just above 100. Southeasterly winds will continue to advect additional moisture from the Gulf will support dewpoints in the upper 70s. The combination of hot temperatures and humidity will likely support peak heat indices ranging from 105-114. However, increasing cloud cover rain chances Thursday afternoon may suppress temperatures and heat indices, keeping confidence low on any widespread heat index values above 110 degrees. A Heat Advisory or Special Weather Statement may be needed Thursday afternoon.

HiRes models support the development of isolated to scattered showers and thunderstorms along the sea breeze early Thursday afternoon. Additionally, enhanced forcing along an advancing cold front approaching from the northwest will likely result in a line of showers and thunderstorms developing ahead of the front and moving into the area mid to late afternoon. Convective models depict these boundaries colliding roughly along I-69C/US-281 late Thursday afternoon or early Thursday evening. From there, the forecast becomes more uncertain, though central and western portions of the CWA will likely continue to see showers and thunderstorms into Friday morning. Strong to severe thunderstorms will be possible Thursday afternoon, with the primary hazards likely to be damaging winds and heavy rainfall. The Storm Prediction Center has a Marginal Risk (level 1 of 5) for Severe weather roughly along and west of I-69C Thursday and Thursday night.

Another round of showers and thunderstorms is likely Friday afternoon through Saturday morning, as the cold front moves through the area. In the wake of the front, an overrunning pattern looks to set up as southeasterly mid-level flow continues to advect warm moist air from the Gulf into the region. This will likely support widespread stratiform rain, with generally light to moderate rainfall across much of the area, though some heavier bands may develop, especially along the coast.

Widespread rainfall amounts of 2 to 4 inches are possible through Saturday morning, with locally higher amounts up to 6 inches possible. Deep tropical moisture, with PWAT values ranging from 2-2.5 inches and ample instability could result in higher rain rates and flash flooding.

The Weather Prediction Center has Zapata, Jim Hogg, Starr, and western portions of Brooks counties in a Moderate Risk (level 3 of 4) of Excessive Rainfall Thursday. The remainder of Deep South Texas, except for eastern portions of Cameron County, are under a Slight Risk (level 2of 4) for Excessive Rainfall Thursday, with Eastern Cameron County under a Marginal Risk (level 1 of 4). Zapata, Starr, Jim Hogg and western portions of Brooks and Hidalgo counties remain under a Slight Risk for Excessive Rainfall Friday with the rest of Deep South Texas under a Marginal Risk for Excessive Rainfall.

AVIATION

(12Z TAFS) Issued at 559 AM CDT Thu Oct 1 2026

MVFR to VFR is anticipated at the aerodromes through the next 24 hours, with moderate to breezy winds and partly to mostly cloudy skies.

MARINE

Issued at 1111 PM CDT Wed Sep 30 2026

Winds and seas along the Lower Texas Coast are forecast to remain elevated Thursday, with Small Craft Should Exercise Caution headlines likely needed through the day. Conditions look to improve Friday morning, with a cold front forecast to move through the area Friday evening. Light northeasterly winds behind the front will likely lower seas through the weekend.

Rain chances are forecast to increase Thursday afternoon, with widespread rainfall likely through the weekend.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 97 80 94 77 / 30 50 80 80 HARLINGEN 99 77 95 72 / 40 60 90 80 MCALLEN 102 79 94 77 / 50 70 80 90 RIO GRANDE CITY 102 76 90 73 / 70 90 90 90 SOUTH PADRE ISLAND 90 82 88 80 / 20 40 60 80 BAYVIEW/PORT ISABEL 95 79 92 76 / 30 40 80 80

BRO WATCHES/WARNINGS/ADVISORIES

None.