textproduct: Houston/Galveston

KEY MESSAGES

- Life-threatening heat will impact southeast Texas today as heat indices climb to 114. An Extreme Heat Warning is in effect through 10 pm.

- Dangerous heat will continue through the weekend, with heat indices in the 108 to 110 range. Limited cooling overnight will exacerbate the heat.

- Scattered showers and thunderstorms are possible on Friday and Saturday, with the potential for locally heavy rainfall. There is a Slight Risk (Level 2 out of 4) of Excessive Rainfall Friday and Friday night.

DISCUSSION

Issued at 107 PM CDT Thu Jun 18 2026

Broad upper troughing will persist over much of the CONUS, with ridging building over the Gulf. Strong southerly flow over the local area continues to filter an abundance of moisture across the area. Meanwhile, mostly clear skies have allowed temps to soar into the lower 90s. Temps may climb another degree or two this afternoon. Combined with dewpoints in the upper 70s, RH values are quite moist. Heat indices are already in the Heat Advisory range (108-113) and these should max out around 115 this afternoon. Given this, an Extreme Heat Warning is in effect for the entire area through this evening.

Heat concerns will continue into the weekend, as the moist airmass remains over the area. There will be enough heating each day for temps to rise into the lower 90s. One caveat will be Friday into Saturday, when a southern stream trough tries to move through the area. That said, given the warmer dewpoints, overnight lows will remain in the upper 70s to lower 80s through Saturday night. This will provide little in the way of cooling and the risk for heat illnesses may compound each day. Due to the lower confidence with the trough building in, a Heat Advisory is in effect through Saturday night. If the clouds/rain don't pan out, we may have to explore more Extreme Heat products this weekend.

Turning our attention to the potential rain Friday afternoon into Saturday, guidance is in a bit of a disagreement on where the trough will move and, therefore, where the heavier rain will set up. The moist airmass persists, with PWs well above normal, so there is a potential for locally heavy rainfall. The area remains wet from previous days rain, so any additional heavy rain will quickly become a flooding concern. Low confidence on timing and location, but it's a concern to monitor over the next 24 hours.

Beyond Sunday, we will likely be in a more typical summer pattern, with high pressure building in and little to no rain chances. The deep layer moisture transport may be more limited and reduce the risk of heat.

AVIATION

(12Z TAF Issuance) Issued at 600 AM CDT Thu Jun 18 2026

Mix of CIGS ranging from MVFR to LIFR span across the region this morning. IFR/LIFR most common north/northwest of the Houston area, with MVFR/isolated IFR to the south. Patchy fog/mist has also developed, largely around 2-6 SM for most areas. CIG/VIS should scatter/lift with daytime heating. VFR conditions should return by the late morning/early afternoon with light to moderate southerly winds. Some light showers linger but otherwise conditions should remain dry. Winds ease down slightly in the evening as MVFR CIGs start to fill in from the coast, slightly soon that yesterday/today. Could see another brief window of IFR/lower FLs early Friday morning.

03

MARINE

Issued at 124 PM CDT Wed Jun 17 2026

Light to moderate southerly winds and sea up to 6ft are expected today and persist into the weekend. Caution flags could be warranted at times over the next few days as the pressure gradient tightens.

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 95 79 93 78 / 0 0 30 50 Houston (IAH) 95 81 93 79 / 0 0 20 30 Galveston (GLS) 90 84 90 84 / 0 0 0 20

HGX WATCHES/WARNINGS/ADVISORIES

TX...Extreme Heat Warning until 8 PM CDT this evening for TXZ163-164- 176>179-195>200-210>214-226-227-235>238-300-313-335>338-436- 438-439.

Heat Advisory from 8 PM this evening to 10 PM CDT Saturday for TXZ163-164-176>179-195>200-210>214-226-227-235>238-300-313- 335>338-436>439.

GM...None.