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

San Marcos, San Marcos Municipal Airport (KHYI)

Lat: 29.89°NLon: 97.86°WElev: 597ft.

Fair

72°F

22°C

Humidity 94%
Wind Speed Calm
Barometer 30.03 in (1016.2 mb)
Dewpoint 70°F (21°C)
Visibility 10.00 mi
Last update 19 Sep 3:56 am CDT
Extended Forecast for

San Marcos TX

  • Today

    Today: Mostly sunny, with a high near 97. Heat index values as high as 101. Calm wind becoming south southeast around 5 mph in the afternoon.

    High: 97 °F

    Mostly Sunny

  • Tonight

    Tonight: Increasing clouds, with a low around 73. Southeast wind around 5 mph becoming south southwest after midnight.

    Low: 73 °F

    Increasing
    Clouds

  • Sunday

    Sunday: Mostly sunny, with a high near 98. Heat index values as high as 103. Calm wind becoming south around 5 mph.

    High: 98 °F

    Mostly Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 75. South southeast wind around 5 mph becoming calm after midnight.

    Low: 75 °F

    Partly Cloudy

  • Monday

    Monday: Sunny, with a high near 97. Calm wind becoming east southeast around 5 mph.

    High: 97 °F

    Sunny

  • Monday Night

    Monday Night: Mostly clear, with a low around 75. East southeast wind around 5 mph becoming calm in the evening.

    Low: 75 °F

    Mostly Clear

  • Tuesday

    Tuesday: A 20 percent chance of showers before 1pm. Sunny, with a high near 97. Calm wind becoming east around 5 mph in the afternoon.

    High: 97 °F

    Slight Chance
    Showers

  • Tuesday Night

    Tuesday Night: A slight chance of showers and thunderstorms. Mostly clear, with a low around 75. East southeast wind around 5 mph becoming calm in the evening. Chance of precipitation is 20%.

    Low: 75 °F

    Slight Chance
    T-storms

  • Wednesday

    Wednesday: Mostly sunny, with a high near 97. North northeast wind around 5 mph becoming east in the afternoon.

    High: 97 °F

    Mostly Sunny

Detailed Forecast

Today
Mostly sunny, with a high near 97. Heat index values as high as 101. Calm wind becoming south southeast around 5 mph in the afternoon.
Tonight
Increasing clouds, with a low around 73. Southeast wind around 5 mph becoming south southwest after midnight.
Sunday
Mostly sunny, with a high near 98. Heat index values as high as 103. Calm wind becoming south around 5 mph.
Sunday Night
Partly cloudy, with a low around 75. South southeast wind around 5 mph becoming calm after midnight.
Monday
Sunny, with a high near 97. Calm wind becoming east southeast around 5 mph.
Monday Night
Mostly clear, with a low around 75. East southeast wind around 5 mph becoming calm in the evening.
Tuesday
A 20 percent chance of showers before 1pm. Sunny, with a high near 97. Calm wind becoming east around 5 mph in the afternoon.
Tuesday Night
A slight chance of showers and thunderstorms. Mostly clear, with a low around 75. East southeast wind around 5 mph becoming calm in the evening. Chance of precipitation is 20%.
Wednesday
Mostly sunny, with a high near 97. North northeast wind around 5 mph becoming east in the afternoon.
Wednesday Night
Partly cloudy, with a low around 74.
Thursday
Mostly sunny, with a high near 96.
Thursday Night
Partly cloudy, with a low around 72.
Friday
Mostly sunny, with a high near 96.
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ABOUT THIS FORECAST

 
Point Forecast:
San Marcos TX
 29.88°N 97.94°W (Elev. 577 ft)
Last Update:
2:44 am CDT Sep 19, 2026
Forecast Valid:
4am CDT Sep 19, 2026-6pm CDT Sep 25, 2026
 
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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