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

Heavy Rain From the Plains to the Northeast; Heat Wave Begins

Severe thunderstorms and heavy rainfall are likely across parts of the Northeast, portions of the northern and central Plains, and the Ohio Valley. Portions of northeast Missouri and central Illinois could experience locally significant flash flooding. Dangerously hot conditions are expected in the Central Plains, Lower and Middle Mississippi Valley, and Southeast. Read More >

Current conditions at

San Marcos, San Marcos Municipal Airport (KHYI)

Lat: 29.89°NLon: 97.86°WElev: 597ft.

A Few Clouds

87°F

31°C

Humidity 65%
Wind Speed S 14 G 20 mph
Barometer 30.08 in (1017.8 mb)
Dewpoint 74°F (23°C)
Visibility 10.00 mi
Heat Index95°F (35°C)
Last update 20 Jul 12:56 pm CDT
Extended Forecast for

San Marcos TX

  • This Afternoon

    This Afternoon: Partly sunny, with a high near 93. Heat index values as high as 100. South wind around 15 mph, with gusts as high as 25 mph.

    High: 93 °F

    Partly Sunny

  • Tonight

    Tonight: Mostly cloudy, with a low around 76. South wind 5 to 15 mph, with gusts as high as 20 mph.

    Low: 76 °F

    Mostly Cloudy

  • Monday

    Monday: Partly sunny, with a high near 97. Heat index values as high as 102. South wind 5 to 10 mph, with gusts as high as 20 mph.

    High: 97 °F

    Partly Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 75. South southeast wind 5 to 10 mph, with gusts as high as 20 mph.

    Low: 75 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Partly sunny, with a high near 96. South wind 5 to 10 mph, with gusts as high as 20 mph.

    High: 96 °F

    Partly Sunny

  • Tuesday Night

    Tuesday Night: Mostly cloudy, with a low around 75. South southeast wind 5 to 10 mph, with gusts as high as 20 mph.

    Low: 75 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: Mostly sunny, with a high near 97. South wind 5 to 10 mph.

    High: 97 °F

    Mostly Sunny

  • Wednesday Night

    Wednesday Night: Mostly clear, with a low around 75. South southeast wind around 5 mph.

    Low: 75 °F

    Mostly Clear

  • Thursday

    Thursday: Sunny, with a high near 97. South wind around 5 mph.

    High: 97 °F

    Sunny

Detailed Forecast

This Afternoon
Partly sunny, with a high near 93. Heat index values as high as 100. South wind around 15 mph, with gusts as high as 25 mph.
Tonight
Mostly cloudy, with a low around 76. South wind 5 to 15 mph, with gusts as high as 20 mph.
Monday
Partly sunny, with a high near 97. Heat index values as high as 102. South wind 5 to 10 mph, with gusts as high as 20 mph.
Monday Night
Partly cloudy, with a low around 75. South southeast wind 5 to 10 mph, with gusts as high as 20 mph.
Tuesday
Partly sunny, with a high near 96. South wind 5 to 10 mph, with gusts as high as 20 mph.
Tuesday Night
Mostly cloudy, with a low around 75. South southeast wind 5 to 10 mph, with gusts as high as 20 mph.
Wednesday
Mostly sunny, with a high near 97. South wind 5 to 10 mph.
Wednesday Night
Mostly clear, with a low around 75. South southeast wind around 5 mph.
Thursday
Sunny, with a high near 97. South wind around 5 mph.
Thursday Night
Partly cloudy, with a low around 75.
Friday
Mostly sunny, with a high near 96.
Friday Night
Partly cloudy, with a low around 76.
Saturday
Mostly sunny, with a high near 94.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
San Marcos TX
 29.9°N 97.91°W (Elev. 640 ft)
Last Update:
1:10 pm CDT Jul 20, 2025
Forecast Valid:
1pm CDT Jul 20, 2025-6pm CDT Jul 26, 2025
 
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Additional Resources

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