textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 544 PM CDT Mon May 18 2026

Key Messages:

* Heat Risk for today and tomorrow is a mixture of moderate and major.

* Strong to severe thunderstorms along with heavy rainfall and localized flooding is possible starting Wednesday through Friday.

* A Small Craft Advisory has been extended till 9 AM CDT Tuesday; a High Risk for Rip Currents continues through Tuesday evening as well.

DISCUSSION

Issued at 1242 PM CDT Mon May 18 2026

While the heat will continue to linger as a potential hazard with high temperatures in the upper 90s to lower triple digits for today and tomorrow. The high temperatures for Wednesday do slightly lower to mostly in the mid 90s as cloud coverage starts to increase, which will be further discussed later on. The heat indices for today and tomorrow do generally float around 108 F. While still below the Heat Advisory criteria, the heat risk for today and tomorrow is moderate (level 2 of 4) and major (level 3 of 4). Thus it will still be important to practice heat safety when possible especially to those that are vulnerable to heat related illnesses.

By Wednesday, cloud coverage is expected to increase over the region as a frontal boundary stalls to the north of the region. With the combination of southwesterly flow aloft, southeasterly flow at the surface, and the frontal boundary to the north. The environment will become more favorable for the development of showers and thunderstorms. As of this current forecast the best chances for rain are on Thursday and Friday with rain chances between 60 to 80% during those days. While chances are generally medium (around 50%) for Wednesday and the rest of the forecast period. Currently the Weather Prediction Center does have all of Deep South Texas and the Rio Grande Valley in a Marginal Risk (level 1 of 4) for Excessive Rainfall days 3 through 5, which covers Wednesday morning through Saturday morning. Thus it will be possible to see some flooding due to the rainfall. The Storm Prediction Center also has a Marginal Risk (level 1 of 5) for severe weather for mostly the Upper Valley for Tuesday through Wednesday. However the rest of the region is in a general thunderstorm outlook thus it is possible for showers and thunderstorms to occur all over the area that day.

Lastly for the coastal hazards, while the Coastal Flood Statement was allowed to expire early this afternoon, but it is possible that another Coastal Flood Statement might be needed tonight. A High Risk of Rip Currents is in effect through Tuesday evening.

AVIATION

(00Z TAFS) Issued at 544 PM CDT Mon May 18 2026

Through 00z Wednesday....VFR-MVFR conditions will prevail through the 00z TAF cycle. VFR conditions will be more prevalent during the afternoon-evening hours with MVFR conditions more prevalent during the night-morning hours.

Breezy southeast winds will continue through the forecast period with speeds between 10-17 knots and gusts between 20-25 knots or so.

MARINE

Issued at 1242 PM CDT Mon May 18 2026

Hazardous marine conditions are expected to persist through most of tonight and into early tomorrow morning, thus a Small Craft Advisory remains in effect until 9 AM tomorrow. Even after the Small Craft Advisory does expire tomorrow morning, adverse conditions are still expected for most of the day tomorrow as seas will take more time to come down. Showers and thunderstorms are expected to return to the region by Wednesday and will continue to persist through the forecast period.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 81 94 81 92 / 10 10 20 0 HARLINGEN 79 95 79 93 / 10 0 20 0 MCALLEN 81 97 80 94 / 20 10 30 10 RIO GRANDE CITY 79 98 78 94 / 20 10 40 30 SOUTH PADRE ISLAND 81 86 81 85 / 10 10 20 0 BAYVIEW/PORT ISABEL 81 92 81 90 / 10 0 20 0

BRO WATCHES/WARNINGS/ADVISORIES

TX...High Rip Current Risk through Tuesday evening for TXZ451-454-455.

GM...Small Craft Advisory until 9 AM CDT Tuesday for GMZ130-132-135- 150-155-170-175.