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

80°F

27°C

Humidity 71%
Wind Speed S 8 mph
Barometer 29.98 in (1014.1 mb)
Dewpoint 70°F (21°C)
Visibility 10.00 mi
Heat Index83°F (28°C)
Last update 27 Aug 4:56 am CDT
Extended Forecast for

San Marcos TX

Heat Advisory August 27, 05:03am until August 27, 07:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory August 27, 05:03am until August 27, 07:00pm

    NOW until 7:00pm Thu

    Heat Advisory

  • Today

    High: 102 °F

    Mostly Sunny
    then Chance
    T-storms

  • Tonight

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

    Low: 76 °F

    Chance
    T-storms then
    Slight Chance
    Showers

  • Friday

    Friday: A 20 percent chance of showers and thunderstorms after 4pm. Mostly sunny and hot, with a high near 99. Heat index values as high as 105. Calm wind becoming east around 5 mph in the afternoon.

    High: 99 °F

    Mostly Sunny
    then Slight
    Chance
    T-storms

  • Friday Night

    Friday Night: A 10 percent chance of showers and thunderstorms before 7pm. Mostly clear, with a low around 76. East southeast wind around 5 mph becoming calm in the evening.

    Low: 76 °F

    Slight Chance
    T-storms then
    Mostly Clear

  • Saturday

    Saturday: Sunny, with a high near 98. Calm wind becoming east southeast around 5 mph in the afternoon.

    High: 98 °F

    Sunny

  • Saturday Night

    Saturday Night: Mostly clear, with a low around 76. South wind around 5 mph.

    Low: 76 °F

    Mostly Clear

  • Sunday

    Sunday: Sunny, with a high near 98. Calm wind becoming south southeast around 5 mph in the morning.

    High: 98 °F

    Sunny

  • Sunday Night

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

    Low: 75 °F

    Mostly Clear

Detailed Forecast

Today
A 30 percent chance of showers and thunderstorms after 1pm. Mostly sunny and hot, with a high near 102. Heat index values as high as 108. Southwest wind around 5 mph becoming calm in the afternoon.
Tonight
A chance of showers and thunderstorms before 10pm, then a slight chance of showers between 10pm and 1am. Mostly cloudy, with a low around 76. South wind around 5 mph becoming calm in the evening. Chance of precipitation is 30%.
Friday
A 20 percent chance of showers and thunderstorms after 4pm. Mostly sunny and hot, with a high near 99. Heat index values as high as 105. Calm wind becoming east around 5 mph in the afternoon.
Friday Night
A 10 percent chance of showers and thunderstorms before 7pm. Mostly clear, with a low around 76. East southeast wind around 5 mph becoming calm in the evening.
Saturday
Sunny, with a high near 98. Calm wind becoming east southeast around 5 mph in the afternoon.
Saturday Night
Mostly clear, with a low around 76. South wind around 5 mph.
Sunday
Sunny, with a high near 98. Calm wind becoming south southeast around 5 mph in the morning.
Sunday Night
Mostly clear, with a low around 75. South wind 5 to 10 mph.
Monday
Mostly sunny, with a high near 98. South wind 5 to 10 mph.
Monday Night
Mostly clear, with a low around 75.
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
 29.9°N 97.91°W (Elev. 640 ft)
Last Update:
4:42 am CDT Aug 27, 2026
Forecast Valid:
5am 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