textproduct: Houston/Galveston

KEY MESSAGES

- Isolated to widely scattered showers and thunderstorms today. Highest potential of a shower/storm will be in our northern counties and along the seabreeze in our southern counties.

- Hot temperatures with daily isolated to scattered diurnal thunderstorms through midweek.

- Less humid after midweek following a backdoor frontal boundary.

DISCUSSION

Issued at 104 PM CDT Mon Sep 21 2026

Today is the final full day of astronomical summer and Mother Nature is going to make sure we get our money's worth as temperatures remain well above normal. Our normal high temperature this time of the year is actually in the low 90s...but most of us will see temperatures top out in the mid to upper 90s this afternoon. Some of you will hit the weather lottery though and get a brief reprieve from the heat in the form of isolated showers/storms this afternoon. The CAMs (including me) still insist on popcorn convection beginning around 2pm along the sea breeze and a few hours later along a lingering boundary over portions of the Brazos Valley/Piney Woods. PW values are generally peaking around or just over the 75th percentile (~1.80"), so it wouldn't surprise me to see a few pockets of 1-2" rainfall occuring in a relatively short period of time. Showers/storms will gradually dissipate after sunset with the loss of daytime heating.

Do you remember...the 21st night of September? We actually will be chasing the clouds away as the overnight hours will feature mostly clear skies...but still fairly humid with lows in the mid to upper 70s. There may be a few nights to remember later in the week though! The above normal temperatures and daily rain chances continue through midweek, and this is probably as good of a time as any to mention that the autumnal equinox is tomorrow (Tuesday) at 7:04 PM CDT. Astronomical fall begins with *checks notes* temperatures in the mid to upper 90s...yeah that's about right. Ridge axis and a developing mid-level high dominate the forecast Tuesday and beyond, which means hot and humid conditions will continue through the rest of the week...right...RIGHT?! Not so fast, my friend!

A trough sweeping through the eastern half of the country will push in a backdoor frontal boundary (a front moving in from the northeast) late Wednesday/early Thursday. Drier air filters in behind this front that lasts going into the early part of the weekend, so low temperatures for some of you (mainly northern areas) will feature the upper 60s/low 70s once again. High temperatures will also be slightly "cooler" as we trade out the upper 90s for the low to mid 90s. Of course we can throw in the cliche "bUt iT'S a DrY hEaT", but 90s are still 90s. We're in the realm of this being better than nothing, but it leaves us longing for that first true front...which we'll briefly talk about at the end of this discussion. Moisture/humidity returns on Sunday leading to the return of rain chances into the forecast.

Before we get into our brief beyond the forecast period outlook on a potential real cold front, let's start with the usual disclaimer: it's too early to lock in anything...remember that we are looking at trends this far out, so it's not an official forecast. Looking at both the GFS and Euro ensembles, there is still a statistically notable number of members that reflect below normal temperatures around the first weekend of October. Now again this doesn't mean that this WILL happen, but it is within the realistic realm of possibilities for once. This is a lot better than the 0% potential we've had over the past five-ish months!

Batiste

AVIATION

(18Z TAF Issuance) Issued at 104 PM CDT Mon Sep 21 2026

Winds are variable throughout our region as a weak boundary to the northwest and afternoon sea breeze to the southeast interact. These two boundaries slightly elevate TS/SH chances, particularly south of I-10 this afternoon and then north of CXO early this evening. Upper level ridging and PWATs less than 2 inches suggest any storms/showers that do develop will be isolated in coverage, resulting in PROB30s throughout most TAF sites. More northern sites around CLL could see elevated coverage (isolated-scattered) with that northern boundary drifting deeper into our region this evening. Current trends suggest that neither boundary will advance close enough to IAH to include them in our PROB30 for the time being. Winds become light and variable by 01-03Z before increasing to 5-10 kts generally out of the northeast by 16Z Tuesday. Patchy fog is possible around sunrise for typical sites (LBX, CXO). Late morning MVFR ceilings possible with a typical summertime cumulus field developing before lifting early Tuesday afternoon. Another round of TS/SH possible Tuesday after 18Z with the sea breeze, which pulls winds back out of the SE by the end of this forecast period.

BSM

MARINE

Issued at 104 PM CDT Mon Sep 21 2026

Light to occasionally moderate east to southeast winds today will become more northeasterly to easterly beginning on Tuesday. Winds may be consistently moderate enough to warrant periods of caution flags at times, especially around midweek. Seas will remain mainly in the 1-3 ft range through the end of the work week, then increasing to 2-4 ft over the weekend. Daily chances for isolated to scattered showers/storms persist through midweek.

Batiste

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 75 98 76 98 / 30 20 10 0 Houston (IAH) 78 97 79 96 / 0 20 10 0 Galveston (GLS) 82 92 83 91 / 0 20 20 10

HGX WATCHES/WARNINGS/ADVISORIES

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