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

Tropical Storm Arthur and Heavy Rainfall in the South; Severe Weather in the Midwest

An outbreak of severe thunderstorms is expected across portions of Illinois and Indiana tonight. Intense tornadoes, swaths of damaging gusts, and hail in excess of 2 inches in diameter possible. Tropical Storm Arthur will continue to produce strong winds across coastal Upper Texas and Louisiana tonight, as well as potentially life-threatening flooding across southern Louisiana into Mississippi. Read More >

Hazardous Weather Conditions

Current conditions at

San Marcos, San Marcos Municipal Airport (KHYI)

Lat: 29.89°NLon: 97.86°WElev: 597ft.

Fair

75°F

24°C

Humidity 96%
Wind Speed Calm
Barometer 29.65 in (1003.1 mb)
Dewpoint 74°F (23°C)
Visibility 10.00 mi
Last update 18 Jun 3:56 am CDT
Extended Forecast for

5 Miles W San Marcos TX

Extreme Heat Warning June 18, 12:00pm until June 18, 08:00pm
Click here for hazard details and duration
Extreme Heat Warning

  • Today

    Today: Partly sunny, then gradually becoming sunny, with a high near 97. Heat index values as high as 113. South wind 5 to 10 mph, with gusts as high as 20 mph.

    High: 97 °F

    Becoming
    Sunny

  • Tonight

    Tonight: Increasing clouds, with a low around 79. Southeast wind around 10 mph, with gusts as high as 20 mph.

    Low: 79 °F

    Increasing
    Clouds

  • Juneteenth

    Juneteenth: A 20 percent chance of showers and thunderstorms after 1pm. Partly sunny, with a high near 93. Heat index values as high as 107. Southeast wind 5 to 10 mph, with gusts as high as 20 mph.

    High: 93 °F

    Mostly Cloudy
    then Slight
    Chance
    T-storms

  • Friday Night

    Friday Night: A chance of showers and thunderstorms before 10pm, then a chance of showers between 10pm and 1am, then a chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 77. Southeast wind 5 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 40%.

    Low: 77 °F

    Chance
    T-storms

  • Saturday

    Saturday: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1pm. Partly sunny, with a high near 90. South wind 5 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 60%.

    High: 90 °F

    Chance
    T-storms then
    Showers
    Likely

  • Saturday Night

    Saturday Night: A chance of showers and thunderstorms before 10pm, then a chance of showers between 10pm and 1am, then a slight chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 76. South wind 5 to 10 mph. Chance of precipitation is 40%.

    Low: 76 °F

    Chance
    T-storms then
    Chance
    Showers

  • Sunday

    Sunday: Mostly sunny, with a high near 93. South wind 10 to 15 mph, with gusts as high as 25 mph.

    High: 93 °F

    Mostly Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 76. South southeast wind around 15 mph, with gusts as high as 25 mph.

    Low: 76 °F

    Partly Cloudy

  • Monday

    Monday: Mostly sunny, with a high near 93. South wind 10 to 15 mph, with gusts as high as 25 mph.

    High: 93 °F

    Mostly Sunny

Detailed Forecast

Today
Partly sunny, then gradually becoming sunny, with a high near 97. Heat index values as high as 113. South wind 5 to 10 mph, with gusts as high as 20 mph.
Tonight
Increasing clouds, with a low around 79. Southeast wind around 10 mph, with gusts as high as 20 mph.
Juneteenth
A 20 percent chance of showers and thunderstorms after 1pm. Partly sunny, with a high near 93. Heat index values as high as 107. Southeast wind 5 to 10 mph, with gusts as high as 20 mph.
Friday Night
A chance of showers and thunderstorms before 10pm, then a chance of showers between 10pm and 1am, then a chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 77. Southeast wind 5 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 40%.
Saturday
A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1pm. Partly sunny, with a high near 90. South wind 5 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 60%.
Saturday Night
A chance of showers and thunderstorms before 10pm, then a chance of showers between 10pm and 1am, then a slight chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 76. South wind 5 to 10 mph. Chance of precipitation is 40%.
Sunday
Mostly sunny, with a high near 93. South wind 10 to 15 mph, with gusts as high as 25 mph.
Sunday Night
Partly cloudy, with a low around 76. South southeast wind around 15 mph, with gusts as high as 25 mph.
Monday
Mostly sunny, with a high near 93. South wind 10 to 15 mph, with gusts as high as 25 mph.
Monday Night
Mostly clear, with a low around 75.
Tuesday
A 20 percent chance of showers and thunderstorms. Partly sunny, with a high near 92.
Tuesday Night
Partly cloudy, with a low around 74.
Wednesday
Mostly sunny, with a high near 92.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
5 Miles W San Marcos TX
 29.88°N 98.02°W (Elev. 797 ft)
Last Update:
3:44 am CDT Jun 18, 2026
Forecast Valid:
4am CDT Jun 18, 2026-6pm CDT Jun 24, 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