National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce

Hazardous Weather Conditions

Current conditions at

San Marcos, San Marcos Municipal Airport (KHYI)

Lat: 29.89°NLon: 97.86°WElev: 597ft.

Fair

103°F

39°C

Humidity 26%
Wind Speed Calm
Barometer 29.97 in (1013.8 mb)
Dewpoint 62°F (17°C)
Visibility 10.00 mi
Heat Index105°F (41°C)
Last update 22 Aug 4:56 pm CDT
Extended Forecast for

San Marcos TX

Heat Advisory August 22, 05:19pm until August 23, 07:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory August 22, 05:19pm until August 23, 07:00pm

    NOW until 7:00pm Sun

    Heat Advisory

  • Tonight

    Low: 77 °F

    Mostly Clear

  • Sunday

    Sunday: Sunny and hot, with a high near 103. Southwest wind around 5 mph becoming south southeast in the afternoon.

    High: 103 °F

    Hot

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 75. South southwest wind 5 to 10 mph.

    Low: 75 °F

    Mostly Clear

  • Monday

    Monday: Sunny and hot, with a high near 102. Heat index values as high as 105. Southwest wind around 5 mph.

    High: 102 °F

    Hot

  • Monday Night

    Monday Night: Mostly clear, with a low around 76. South southeast wind 5 to 10 mph, with gusts as high as 20 mph.

    Low: 76 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny and hot, with a high near 102. South southwest wind around 5 mph.

    High: 102 °F

    Hot

  • Tuesday Night

    Tuesday Night: Clear, with a low around 76. South southeast wind 5 to 10 mph.

    Low: 76 °F

    Clear

  • Wednesday

    Wednesday: Sunny and hot, with a high near 103. South southwest wind around 5 mph.

    High: 103 °F

    Hot

Detailed Forecast

Tonight
Mostly clear, with a low around 77. South southeast wind around 5 mph becoming southwest after midnight.
Sunday
Sunny and hot, with a high near 103. Southwest wind around 5 mph becoming south southeast in the afternoon.
Sunday Night
Mostly clear, with a low around 75. South southwest wind 5 to 10 mph.
Monday
Sunny and hot, with a high near 102. Heat index values as high as 105. Southwest wind around 5 mph.
Monday Night
Mostly clear, with a low around 76. South southeast wind 5 to 10 mph, with gusts as high as 20 mph.
Tuesday
Sunny and hot, with a high near 102. South southwest wind around 5 mph.
Tuesday Night
Clear, with a low around 76. South southeast wind 5 to 10 mph.
Wednesday
Sunny and hot, with a high near 103. South southwest wind around 5 mph.
Wednesday Night
Mostly clear, with a low around 77. South wind around 5 mph.
Thursday
Sunny and hot, with a high near 102.
Thursday Night
A 20 percent chance of showers and thunderstorms. Partly cloudy, with a low around 78.
Friday
Mostly sunny and hot, with a high near 100.
Friday Night
Mostly clear, with a low around 78.
Saturday
Sunny and hot, with a high near 99.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
San Marcos TX
 29.88°N 97.94°W (Elev. 577 ft)
Last Update:
4:42 pm CDT Aug 22, 2026
Forecast Valid:
5pm CDT Aug 22, 2026-6pm CDT Aug 29, 2026
 
Forecast Discussion
 
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Additional Resources

Radar & Satellite Image

Link to Local Radar Data Link to Satellite Data

Hourly Weather Forecast

National Digital Forecast Database

National Digital Forecast Database Maximum Temperature Forecast

High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation