textproduct: Austin/San Antonio

KEY MESSAGES

- Hazardous heat expected Thursday across South-Central Texas.

- Hot and humid weather continues into next week.

- Isolated rain chances Thursday night with broader chances Friday night into Saturday.

SHORT TERM

(Tonight through Thursday night) Issued at 1220 PM CDT Wed Jun 17 2026

A large and anomalous mass of hot air is currently spreading across Texas, harboring temperatures at about 10 kft altitude reaching the 97th percentile or warmer for mid-June. The upper-air sounding at Del Rio recorded a substantial 4-degree rise at that height between the 00Z and 12Z launch this morning, so the core of that hot air is beginning to filter into South-Central Texas. Drier air aloft and subsidence is allowing that heat to impress upon the Rio Grande and Hill Country, and is subduing the effects of nearby Tropical Storm Arthur in our eastern counties to just some cloudiness and perhaps a few passing showers along Highway 77.

Hazardous heat is anticipated throughout South-Central Texas Thursday as the core of the incoming hot air shifts over the region. A low-pressure area formed by intense heating over the Texas panhandle is also expected to drop south increase the flow of humid tropical air over our area during the day. The combination of high temperatures and tropical humidity will produce hazardous heat conditions. Apparent temperatures should top 100F by noon for most areas, with peak values reaching the 110F to 115F range south and east of the Balcones Escarpment, and 105F to 112F over the Edwards Plateau and Hill Country. A few locations within the Rio Grande Plains may see heat indices remaining above 100F as late as 1 AM early Friday morning. An Extreme Heat Warning will go into effect Thursday for the I-35 corridor, Coastal Plains, and southern Rio Grande Plains. A Heat Advisory will go into effect for the Hill Country, Edwards Plateau, and northern Rio Grande Plains. These products differentiate the magnitude of the heat due to slight differences in moisture, but the message for all of South-Central Texas is the same: the heat during the day Thursday will likely be hazardous if precautions are not taken. Stay hydrated and cool, and limit strenuous time outdoors. Additional safety information is available at weather.gov/heat.

There is some chance, about 20 to 30 percent, that isolated thunderstorms may develop to our north late Thursday and could push across portions of the Edwards Plateau early Friday morning. Wind shear remains weak and should limit the intensity of these storms, but some lightning is possible.

LONG TERM

(Friday through next Wednesday) Issued at 1220 PM CDT Wed Jun 17 2026

The onshore flow is expected to weaken slightly Friday, with the hot airmass not as concentrated. While this decreases apparent temperatures somewhat, it will likely remain hot with heat indices above 105F for many areas, especially along the I-35 corridor and Coastal Plains. Additional Heat Advisories may be needed for Friday.

A weak frontal zone also approaches our area from the north on Friday, diffusing over our area Friday into Saturday. A few thunderstorms developing over North Texas could send outflow boundaries south towards our area, which may aid in increasing rain chances starting Friday. Broad divergence ahead of a passing trough may also spark additional storm development along the dry line over the Edwards Plateau. There are some indications that an MCS could develop along the dry line on the southern end of the mid-level trough near or over the Edwards Plateau and Hill Country sometime late Friday into Saturday, fueled by the high heat and humidity. If a complex of storms can get established, locally heavy rain is possible given weak deep- layer flow (less than 10 kt) and 1.6-1.8 inch PWATs. Rain chances could linger into Saturday and perhaps even Sunday as well, depending on whether remnant vorticity sticks around over the area from the initial developments on Friday as moist onshore flow remains available. Zonal flow becomes better established next week as subtropical ridging links up over the SW US and Gulf, resulting in a reduction in rain chances heading into next week.

The rains may bring slight thermal relief, reducing heat from the higher-end values, but the overall hot and humid airmass should stay mostly intact heading into the weekend and through the start of next week. Both the air temperature and the dew point are expected to remain above average through the next seven days both by day and by night, and additional heat-related advisories or warnings could be issued.

AVIATION

(18Z TAFS) Issued at 1220 PM CDT Wed Jun 17 2026

MVFR ceilings will persist another hour or two this afternoon for KAUS and locations eastward into the coastal plains with the outer cloud cover associated with Tropical Storm Arthur. Clouds will then scatter our with bases raising to around 4000 feet. Locations that are farther west, including the San Antonio terminals and KDRT, feature few clouds to sky clear conditions through the evening. For the overnight into early Thursday, MVFR to IFR ceilings establish across the I-35 terminals (KAUS, KSAT, and KSSF). Expect for the flight conditions then improve into Thursday afternoon as clouds scatter out and bases rise. The winds remain light for most, with directions becoming more east-southeasterly through this afternoon then more southeasterly through tonight as Tropical Storm Arthur advances farther away to the northeast. Winds tread breeziest across the Rio Grande, including KDRT, this afternoon with gusts at high as 20 to 25 kt.

PRELIMINARY POINT TEMPS/POPS

Austin Camp Mabry 78 96 80 92 / 0 0 20 10 Austin Bergstrom Intl Airport 79 96 80 92 / 0 0 10 10 New Braunfels Muni Airport 77 96 79 92 / 0 0 10 10 Burnet Muni Airport 77 95 78 91 / 0 0 30 10 Del Rio Intl Airport 78 103 81 95 / 0 0 30 30 Georgetown Muni Airport 77 95 79 91 / 0 0 20 20 Hondo Muni Airport 77 97 79 94 / 0 0 20 10 San Marcos Muni Airport 77 95 79 92 / 0 0 10 10 La Grange - Fayette Regional 78 95 80 93 / 0 0 10 10 San Antonio Intl Airport 78 96 80 92 / 0 0 10 10 Stinson Muni Airport 78 96 79 93 / 0 0 10 10

EWX WATCHES/WARNINGS/ADVISORIES

Heat Advisory from noon to 8 PM CDT Thursday for TXZ171-172- 183>190-202.

Extreme Heat Warning from noon to 8 PM CDT Thursday for TXZ173- 191>194-203>209-217>225-228.