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.

Thunderstorm in Vicinity

103°F

39°C

Humidity 36%
Wind Speed SE 8 mph
Barometer 29.93 in (1012.5 mb)
Dewpoint 71°F (22°C)
Visibility 10.00 mi
Heat Index113°F (45°C)
Last update 27 Aug 2:56 pm CDT
Extended Forecast for

San Marcos TX

Heat Advisory August 27, 03:33pm until August 27, 07:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory August 27, 03:33pm until August 27, 07:00pm

    NOW until 7:00pm Thu

    Heat Advisory

  • This Afternoon

    High: 101 °F

    Chance
    T-storms

  • Tonight

    Tonight: A chance of showers and thunderstorms before 10pm, then a slight chance of showers between 10pm and 1am. Partly cloudy, with a low around 76. Southeast wind around 5 mph becoming calm. Chance of precipitation is 30%.

    Low: 76 °F

    Chance
    T-storms then
    Slight Chance
    Showers

  • Friday

    Friday: Sunny and hot, with a high near 100. Heat index values as high as 107. Calm wind becoming east around 5 mph in the afternoon.

    High: 100 °F

    Hot

  • Friday Night

    Friday Night: Mostly clear, with a low around 76. East wind around 5 mph becoming calm in the evening.

    Low: 76 °F

    Mostly Clear

  • Saturday

    Saturday: Sunny and hot, with a high near 99. Calm wind becoming east southeast around 5 mph in the afternoon.

    High: 99 °F

    Hot

  • Saturday Night

    Saturday Night: Mostly clear, with a low around 75. East southeast wind around 5 mph becoming south after midnight.

    Low: 75 °F

    Mostly Clear

  • Sunday

    Sunday: Sunny and hot, with a high near 99. Calm wind becoming south around 5 mph in the morning.

    High: 99 °F

    Hot

  • Sunday Night

    Sunday Night: Clear, with a low around 74. Southeast wind 5 to 10 mph.

    Low: 74 °F

    Clear

Detailed Forecast

This Afternoon
A 50 percent chance of showers and thunderstorms. Partly sunny and hot, with a high near 101. Heat index values as high as 108. Calm wind. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Tonight
A chance of showers and thunderstorms before 10pm, then a slight chance of showers between 10pm and 1am. Partly cloudy, with a low around 76. Southeast wind around 5 mph becoming calm. Chance of precipitation is 30%.
Friday
Sunny and hot, with a high near 100. Heat index values as high as 107. Calm wind becoming east around 5 mph in the afternoon.
Friday Night
Mostly clear, with a low around 76. East wind around 5 mph becoming calm in the evening.
Saturday
Sunny and hot, with a high near 99. Calm wind becoming east southeast around 5 mph in the afternoon.
Saturday Night
Mostly clear, with a low around 75. East southeast wind around 5 mph becoming south after midnight.
Sunday
Sunny and hot, with a high near 99. Calm wind becoming south around 5 mph in the morning.
Sunday Night
Clear, with a low around 74. Southeast wind 5 to 10 mph.
Monday
Sunny, with a high near 98. South wind around 5 mph.
Monday Night
Mostly clear, with a low around 76.
Tuesday
Mostly sunny and hot, with a high near 99.
Tuesday Night
Mostly clear, with a low around 75.
Wednesday
Mostly sunny, with a high near 98.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
San Marcos TX
 29.88°N 97.91°W (Elev. 597 ft)
Last Update:
2:46 pm CDT Aug 27, 2026
Forecast Valid:
3pm CDT Aug 27, 2026-6pm CDT Sep 2, 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