Webinar on Heavy Rainfall and Flooding Threat for This Week - September 29, 2026

Watch our September 29, 2026, webinar regarding the heavy rainfall and flooding threat for South-Central Texas this week. A new webinar will be available around midday on Wednesday. Read More >

Hazardous Weather Conditions

Flood Watch in effect from September 30, 07:00 PM CDT until October 2, 07:00 PM CDT

Current conditions at

San Marcos, San Marcos Municipal Airport (KHYI)

Lat: 29.89°NLon: 97.86°WElev: 597ft.

Overcast

79°F

26°C

Humidity	88%
Wind Speed	SE 3 mph
Barometer	29.85 in (1009.8 mb)
Dewpoint	75°F (24°C)
Visibility	10.00 mi
Heat Index	83°F (28°C)
Last update	30 Sep 4:56 am CDT

More Information:

Local Forecast Office More Local Wx 3 Day History Hourly Weather Forecast

Extended Forecast for

San Marcos TX

Flood Watch September 30, 07:00pm until October 2, 07:00pm

Click here for hazard details and duration

Flood Watch

Overnight
Low: 76 °F
Slight Chance
T-storms
Wednesday
High: 95 °F
Chance
T-storms
Wednesday Night
Low: 77 °F
Chance
T-storms then
Chance
Showers
Thursday
High: 90 °F
Showers
Likely then
T-storms
Thursday Night
Low: 73 °F
T-storms then
Heavy Rain
Friday
High: 83 °F
Showers
Friday Night
Low: 70 °F
Chance
T-storms then
Chance
Showers
Saturday
High: 81 °F
Chance
Showers
Saturday Night
Low: 69 °F
Slight Chance
T-storms then
Chance
Showers

Detailed Forecast

Overnight

A 20 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 76. South southeast wind around 10 mph.

Wednesday

A 40 percent chance of showers and thunderstorms, mainly after 4pm. Partly sunny, with a high near 95. Heat index values as high as 106. South southeast wind 10 to 15 mph, with gusts as high as 25 mph.

Wednesday Night

A chance of showers and thunderstorms before 7pm, then a chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 77. South southeast wind 10 to 15 mph, with gusts as high as 25 mph. Chance of precipitation is 50%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Thursday

A chance of showers and thunderstorms, then showers and possibly a thunderstorm after 10am. High near 90. South southeast wind 5 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 90%.

Thursday Night

Showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 73. South southeast wind around 5 mph becoming calm. Chance of precipitation is 90%.

Friday

Showers and possibly a thunderstorm. High near 83. Northeast wind around 5 mph. Chance of precipitation is 90%.

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 70. North northeast wind 5 to 10 mph. Chance of precipitation is 50%.

Saturday

A chance of showers, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 81. North wind around 10 mph, with gusts as high as 20 mph. Chance of precipitation is 50%.

Saturday Night

A 40 percent chance of showers and thunderstorms, mainly after 1am. Mostly cloudy, with a low around 69. North northeast wind 5 to 10 mph, with gusts as high as 20 mph.

Sunday

A chance of showers, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 80. Chance of precipitation is 50%.

Sunday Night

A 20 percent chance of showers. Mostly cloudy, with a low around 68.

Monday

A 20 percent chance of showers. Mostly sunny, with a high near 80.

Monday Night

Partly cloudy, with a low around 65.

Tuesday

Sunny, with a high near 81.