textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1236 AM CDT Fri Sep 18 2026

- Low (15-30%) chances of rain near the coast tonight spread further inland and increase to a low to medium (20-40%) chance along/west US-281 by Friday afternoon before diminishing throughout Friday evening.

- Rain chances minimize Friday night into Saturday before gradually increasing and expanding on Sunday to region-wide low to medium chances by possibly next Tuesday.

- Mainly moderate risks of heat-related illnesses (level 2/4) on Friday and Saturday re-escalate to moderate to major (level 3/4) risks by Sunday.

- A moderate risk of life-threatening rip currents continues through Friday afternoon.

DISCUSSION

Issued at 1028 PM CDT Thu Sep 17 2026

Low (15-30%) chances of passing showers along/east I-69 E tonight spread further inland along the seabreeze boundary on Friday, increasing to a low to medium (20-40%) chance along/west US-281 by Friday afternoon as easterly to northeasterly winds flowing about a surface high pressure settling over the Deep South continue to push the back half of a deep Gulf moisture plume westward. Due to above average moisture content anticipated to linger through Friday afternoon, moderate to heavy rain within passing convection is still possible which could lead to brief periods of reduced visibility, slippery roads and nuisance ponding. Additionally, a SPS for heat indices of 108-111 F is possible on Friday for the coastal and inland portions of Cameron, Willacy and Kenedy counties during the afternoon and early evening hours, dependent on cloud coverage, convective development and model trends.

Otherwise, mid- and lower-level moisture is anticipated to dry considerably throughout the remainder of Friday night to near or below average by Saturday morning as a result of sinking air associated with a high pressure aloft centering over the Southern Plains, thus cutting down on rain chances to a less than 10% chance on Saturday and a low (15-20%) across the southern portions of the lower and mid RGV on Sunday. Decreasing cloud cover over the weekend is expected to slightly raise temperatures and expand highs in the lower 100s over the Rio Grande Plains (upper 90s elsewhere) on Friday to most areas along/west I-69 E by Sunday and Monday; mainly moderate risks of heat-related illnesses on Friday and Saturday deteriorate to mostly major by Monday.

Subsidence begins to wane and moisture profiles steadily moisten throughout next week as the high pressure over the Southern Plains becomes wedged between a stationary upper level low over the eastern Gulf and a series of mid/upper level shortwave troughs translating eastward across the Plains. We currently anticipate for low (15-30%) chances of rain along/east US-281 on Monday to expand and build to region-wide low to medium (30-40% or greater) chances by possibly Tuesday, which could also cause temperatures to cool slightly and improve heat risks to mainly moderate by late week. Additional SPSs remain possible.

AVIATION

(06Z TAFS) Issued at 1236 AM CDT Fri Sep 18 2026

VFR will prevail at the aerodromes through the next 24 hours, with light to moderate winds and clear to partly cloudy skies. Isolated convection is possible, but has not been included in this TAF issuance.

MARINE

Issued at 1028 PM CDT Thu Sep 17 2026

Gentle to moderate northeasterly to easterly winds and moderate (3-5 ft) seas continue, becoming easterly to southeasterly winds with slight to moderate (1-3 ft) seas later this weekend. Meanwhile, low to medium chances of rain continue through Friday afternoon before minimizing to low chances into the remainder of this weekend. Low to medium chances of rain return early next week, gradually increasing to a medium chance as the week progresses.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 95 79 95 78 / 20 0 10 0 HARLINGEN 97 75 98 74 / 20 0 10 0 MCALLEN 99 78 100 78 / 30 0 0 0 RIO GRANDE CITY 99 77 101 77 / 20 0 0 0 SOUTH PADRE ISLAND 89 81 89 81 / 30 10 10 0 BAYVIEW/PORT ISABEL 94 78 94 77 / 30 10 10 0

BRO WATCHES/WARNINGS/ADVISORIES

None.