textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1106 PM CDT Sat Sep 19 2026

- Major to Extreme Heat Risk continues across the populated RGV through at least Tuesday, with Moderate to Major across the rural areas where overnight temperatures will be a little lower each day.

- Record heat for the month-to-date will remain the story through the seven day period and beyond.

- Generally dry weather will prevail through Tuesday or Wednesday, with some potential for increased rain chances and coverage by Wednesday or Thursday. That said...overall area- wide rainfall for the week will remain below seasonal averages, which is a little over 1".

DISCUSSION

Issued at 1106 PM CDT Sat Sep 19 2026

The big picture for the next seven days, through the last full week of September 2026? The heat dome refuses to loosen its grip on the southern tip of Texas. After a single-day window of "typical" rainfall (mainly for the upper Valley and Brush Country) on Friday, another slug of dry air followed today, with zero rainfall on a(nother) day when area-wide average rainfall is around 0.20". The dry air remains entrenched Sunday and likely for most on Monday, which means status quo for daytime and overnight temperatures. Perhaps the only good news is that longer nights and calm late night/early morning winds are nudging morning temperatures into the 70s, including the urban areas. Afternoon highs are a smidge lower than a week ago...but still running 6 to 9 degrees above late September averages and will continue to do so through at least Tuesday.

As for Tuesday...NBM is returning better rain chances to the region, but model trends are drying a bit so with the 500 mb ridge still parked over all of Texas, any deeper moisture is likely to remain in Mexico for one more day. On Wednesday, there is a hint that the ridge axis will shift eastward into the western Gulf, which could open the door to a touch more deep-layer moisture and hence a bit more coverage of rain, likely following the mid-late morning start near the coast and reaching farther inland by early to mid afternoon. Thursday may offer the best opportunity for at least "average" coverage for late September, before the ridge slides westward once again Friday into next weekend, with plenty of heat underneath it despite broad low-level east-northeast flow similar to what we're seeing today.

Bottom line? September is locking in on a record-shattering temperature month, along with drier-to-much drier than average (average is 4.5" west to 6" east, and we're sitting at 5-25% of the month-to-date values (about 3.5 to 5")for all but a few pockets.

Finally...that generally persistent broad but not too strong east- northeast flow will maintain a moderate rip current intensity on most days. Such days when the waves are enticing and the surf is warm (mid 80s) can be deceptive to poor swimmers who can get trapped in a rip...so folks venturing to the beach need to be extra vigilant, as we've had more drownings on moderate days than any other type since 2008.

AVIATION

(00Z TAFS) Issued at 534 PM CDT Sat Sep 19 2026

Fair weather and excellent flying conditions...outside of the usual afternoon thermals for smaller aircraft...is the story through late Sunday afternoon. A quiet evening on tap with the usual early evening gusty easterlies settling down to near-calm conditions under mainly clear skies...save for passing few- scattered MVFR fair weather cumulus.

For Sunday morning, expect another period with Gulf and northeast Mexico towering cu and a few cumulonimbus...but the aerodromes should be free of significant clouds to start along with light winds. Like the previous few days, expect a period of cumulus congestus at Brownsville and Harlingen by mid to late morning, continuing through noon or so before the cumulus flattens and pushes inland with mainly clear skies after 2-3 PM. McAllen will start clear and continue through around noon before VFR scattered cumulus arrives, then lifts further with another 100 degree afternoon. Expect the sea breeze, relatively copacetic, to arrive around 19Z in Brownsville, 20Z in Harlingen, and 22/23Z in McAllen...with the occasional gust to 20 knots in well-mixed air at McAllen just before sunset.

MARINE

Issued at 1106 PM CDT Sat Sep 19 2026

Through at least Tuesday, fair conditions with isolated to perhaps scattered mainly overnight-late morning showers is expected. Broad but light to occasionally moderate easterly flow will prevail with the daily sea breeze nudging Laguna Madre winds up to 10-15 knots for a spell between 2 PM and 8 PM most days. Could see a bit more coverage of showers and a few storms Wednesday and Thursday...but nothing more than average for this time of year and confidence is low at this point given no significant forcing mechanism as the persistent upper level ridge dominates. Overall, favorable boating conditions especially given that its September.

CLIMATE

Issued at 1106 PM CDT Sat Sep 19 2026

Here are some staggering temperature numbers for September and Astronomical Summer (June 21 to September 18), which is nearing its end, so far:

Brownsville (since 1878) September 1-18 June 21 - September 18 90.3 (#1, prior: 89.1, 2023) 89.1 (#2, prior: 89.3, 2023)

Harlingen (since 1912) September 1-18 June 21 - September 18 88.4 (#1, prior: 88, 2023) 87.8 (#2, prior: 88.9, 2023)

McAllen (since 1941) September 1-18 June 21 - September 18 92.6 (#1, prior: 89.9, 2023) 91.3 (#1, prior: 90.7, 2009)

Raymondville (since 1913) September 1-18 June 21 - September 18 90.2 (#1, prior: 88.3, 2023) 88.9 (#2, prior: 89.2, 2023)

Weslaco (since 1914) September 1-18 June 21 - September 18 90.3 (#1, prior: 88.8, 2023) 89.1 (#2, prior: 89.3, 2023)

Other interesting statistics: *Brownsville set another maximum temperature record (99) on the 19th. That makes 13 new records in September alone, and 33 for the calendar year so far. *McAllen reached 59 straight 100 degree days, putting more distance between 2026 and the prior record (49) in 2009. *McAllen also reached 89 days with 100 degrees or higher, with the record of 97 (set in 2023) in clear range.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 78 97 79 96 / 0 10 10 30 HARLINGEN 74 100 75 100 / 0 10 0 20 MCALLEN 78 102 79 102 / 0 0 10 30 RIO GRANDE CITY 76 102 77 102 / 0 0 0 10 SOUTH PADRE ISLAND 81 89 82 90 / 0 10 0 10 BAYVIEW/PORT ISABEL 77 95 78 95 / 0 10 0 20

BRO WATCHES/WARNINGS/ADVISORIES

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