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.

Partly Cloudy

78°F

26°C

Humidity 90%
Wind Speed S 7 mph
Barometer 29.89 in (1011.3 mb)
Dewpoint 75°F (24°C)
Visibility 10.00 mi
Heat Index80°F (27°C)
Last update 12 Sep 2:56 am CDT
Extended Forecast for

San Marcos TX

Heat Advisory September 12, 12:00pm until September 12, 07:00pm
Click here for hazard details and duration
Heat Advisory

  • Overnight

    Overnight: Partly cloudy, with a low around 76. South wind around 5 mph.

    Low: 76 °F

    Partly Cloudy

  • Saturday

    Saturday: Mostly sunny and hot, with a high near 101. Heat index values as high as 107. South wind 5 to 10 mph.

    High: 101 °F

    Hot

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 76. South southeast wind 5 to 10 mph, with gusts as high as 20 mph.

    Low: 76 °F

    Partly Cloudy

  • Sunday

    Sunday: Partly sunny, then gradually becoming sunny and hot, with a high near 99. Heat index values as high as 104. South wind 5 to 10 mph, with gusts as high as 20 mph.

    High: 99 °F

    Hot

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 76. South wind 5 to 10 mph, with gusts as high as 20 mph.

    Low: 76 °F

    Partly Cloudy

  • Monday

    Monday: Mostly sunny and hot, with a high near 99. South wind 5 to 10 mph, with gusts as high as 20 mph.

    High: 99 °F

    Hot

  • Monday Night

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

    Low: 76 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Sunny and hot, with a high near 99. South wind 5 to 10 mph, with gusts as high as 20 mph.

    High: 99 °F

    Hot

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 75. Southeast wind 10 to 15 mph becoming light south after midnight. Winds could gust as high as 25 mph.

    Low: 75 °F

    Mostly Clear

Detailed Forecast

Overnight
Partly cloudy, with a low around 76. South wind around 5 mph.
Saturday
Mostly sunny and hot, with a high near 101. Heat index values as high as 107. South wind 5 to 10 mph.
Saturday Night
Partly cloudy, with a low around 76. South southeast wind 5 to 10 mph, with gusts as high as 20 mph.
Sunday
Partly sunny, then gradually becoming sunny and hot, with a high near 99. Heat index values as high as 104. South wind 5 to 10 mph, with gusts as high as 20 mph.
Sunday Night
Partly cloudy, with a low around 76. South wind 5 to 10 mph, with gusts as high as 20 mph.
Monday
Mostly sunny and hot, with a high near 99. South wind 5 to 10 mph, with gusts as high as 20 mph.
Monday Night
Partly cloudy, with a low around 76. South wind 5 to 10 mph, with gusts as high as 20 mph.
Tuesday
Sunny and hot, with a high near 99. South wind 5 to 10 mph, with gusts as high as 20 mph.
Tuesday Night
Mostly clear, with a low around 75. Southeast wind 10 to 15 mph becoming light south after midnight. Winds could gust as high as 25 mph.
Wednesday
Mostly sunny, with a high near 98.
Wednesday Night
Mostly clear, with a low around 75.
Thursday
A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 97.
Thursday Night
Partly cloudy, with a low around 74.
Friday
Mostly sunny, with a high near 96.
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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:
2:44 am CDT Sep 12, 2026
Forecast Valid:
3am CDT Sep 12, 2026-6pm CDT Sep 18, 2026
 
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Additional Resources

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High Temperature

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Chance of Precipitation