textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 453 PM CDT Sun Sep 13 2026

- A Heat Advisory is in effect for the Mid to Lower Rio Grande Valley and the coastal counties today.

- Widespread extreme risks of heat-related illnesses (level 4/4) prevail through Monday, gradually improving from a major (level 3/4) and extreme risk on Tuesday and Wednesday to a mainly moderate (level 2/4) risk by Thursday.

- Isolated showers and thunderstorms are possible this afternoon. Rain chances increase through the later half of the week.

DISCUSSION

Issued at 1242 PM CDT Sun Sep 13 2026

Widespread triple digit high temperatures and heat index values ranging from 108 to 115 degrees will continue to be the primary concern through mid week. A broad upper level high pressure system over the southeastern US will shift further west through mid week,supporting broad subsidence aloft through mid week. This pattern will support generally rain free conditions Monday through Wednesday, though isolated sea breeze convection. Major to Extreme heat risk is forecast to continue through mid-week, and Heat Advisories may be needed each afternoon.

Fire weather may be a concern Tuesday, as afternoon relative humidity values fall to 20-30% across most of the CWA as gusty winds increase through the afternoon. A brief Fire Danger Statement may be needed Tuesday.

A shortwave moving through the southern periphery of the high pressure system will likely increase forcing and mid-level moisture through the later half of the week, leading to increased rain chances Thursday and Friday, with the highest rain chances along the coast. Increased cloud cover through the later half of the week will likely drop high temperatures to the upper 90s to around 100.

AVIATION

(00Z TAFS) Issued at 453 PM CDT Sun Sep 13 2026

Breezy southeasterly winds evening diminish to light to gentle, or variable, later this evening before steadily picking back to around 15 kt, with gusts 20-25+ kt, by tomorrow afternoon. Aside from a low (15-20%) chance of brief isolated showers, perhaps a thunderstorm or two, near KBRO late tonight, VFR conditions prevail.

MARINE

Issued at 1242 PM CDT Sun Sep 13 2026

Generally favorable marine conditions are forecast through the period, though elevated wind speeds along the Laguna Madre may required Small Craft Should Exercise Caution headlines each afternoon through Wednesday. Otherwise, light to moderate winds and slight to moderate seas are forecast to continue. Daily rain chances will continue over the Gulf waters this week, with rain chances increasing and expanding over the Laguna Madre Thursday and Friday.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 81 98 81 98 / 20 10 0 0 HARLINGEN 77 102 77 102 / 10 10 0 0 MCALLEN 81 103 81 104 / 10 0 0 0 RIO GRANDE CITY 79 104 79 105 / 0 0 0 0 SOUTH PADRE ISLAND 82 90 83 90 / 20 10 10 0 BAYVIEW/PORT ISABEL 79 96 79 97 / 10 10 10 0

BRO WATCHES/WARNINGS/ADVISORIES

TX...Heat Advisory until 7 PM CDT this evening for TXZ251>255-351- 353>355.

GM...None.