SAN MARCOS, TX 78666 Weather Forecast & Current Conditions
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  78666 WEATHER WARNINGS (SEVERE T-STORM & TORNADO)
 CURRENT WEATHER

SAN MARCOS, TX
Current Weather
5:56 PM CDT SEP 29, 2026
Clear
93°F
Feels Like: 101°F
Dewpoint: 72°F
Rel. Hum.: 51%
Visibility: 10 miles
Wind: SE at 14 mph
Pressure: 29.78 inches
Last 72 hours

Local Area Snow Depth

Texas Current Weather

Texas MOS Forecast Weather


Regional Weather Maps

(Automated weather data from NWS/FAA)
  78666 WEATHER FORECAST
10-Day model forecast maps
2026 Hurricanes

SAN MARCOS, TX 78666
Weather Forecast

 Snowfall Forecast pages
Snow Depth pages
TONIGHT
Partly cloudy this evening, then becoming mostly cloudy. Lows in the lower 70s. Southeast winds around 10 mph with gusts up to 25 mph.
WEDNESDAY
Mostly cloudy in the morning, then partly cloudy with a slight chance of showers and thunderstorms in the afternoon. Humid with highs in the mid 90s. South winds 10 to 15 mph with gusts up to 30 mph. Chance of rain 20 percent. Highest heat index readings up to 106.
WEDNESDAY NIGHT
Partly cloudy in the evening, then becoming cloudy. A slight chance of thunderstorms. A slight chance of showers in the evening, then a chance of showers after midnight. Some thunderstorms may produce heavy rainfall. Humid with lows in the mid 70s. Southeast winds 10 to 15 mph with gusts up to 30 mph. Chance of rain 50 percent.
THURSDAY
Showers likely with a slight chance of thunderstorms in the morning, then showers with thunderstorms likely in the afternoon. Some thunderstorms may produce heavy rainfall in the morning. Some thunderstorms may produce heavy rainfall in the afternoon. Humid with highs in the upper 80s. South winds 10 to 15 mph with gusts up to 25 mph. Chance of rain near 100 percent.
THURSDAY NIGHT
A chance of thunderstorms. Showers. Some thunderstorms may produce heavy rainfall. Locally heavy rainfall possible after midnight. Lows in the lower 70s. Southeast winds around 5 mph. Chance of rain near 100 percent.
FRIDAY
Showers with a chance of thunderstorms. Some thunderstorms may produce heavy rainfall. Highs in the lower 80s. Chance of rain 90 percent.
FRIDAY NIGHT
Showers. A chance of thunderstorms, mainly in the evening. Lows in the upper 60s. Chance of rain 80 percent.
SATURDAY
Cloudy with showers likely. A slight chance of thunderstorms in the afternoon. Highs around 80. Chance of rain 70 percent.
SATURDAY NIGHT
Mostly cloudy with a 50 percent chance of showers. Lows in the upper 60s.
SUNDAY
Cloudy with a chance of showers. A slight chance of thunderstorms in the afternoon. Highs around 80. Chance of rain 50 percent.
SUNDAY NIGHT
Mostly cloudy with a slight chance of showers. Lows in the mid 60s.
MONDAY
Mostly cloudy. A slight chance of showers in the morning, then a chance of showers with a slight chance of thunderstorms in the afternoon. Highs around 80. Chance of rain 30 percent.
MONDAY NIGHT
Mostly cloudy in the evening, then becoming partly cloudy. Lows in the mid 60s.

  78666 WEATHER SATELLITE LOOPS
Visible Weather Satellite
SAN MARCOS, TX 78666
Infrared Weather Satellite
SAN MARCOS, TX 78666
  78666 WEATHER RADAR LOOP
NEXRAD Weather Radar
SAN MARCOS, TX 78666
 MOS COMPUTER WEATHER FORECAST

SAN MARCOS, TX 3 hourly weather forecast
weather forecast created  8:00 AM EDT  9/29/2026
Tuesday
29 SEP 2026		 SAN MARCOS, TX 78666 weather forecast Day 1, 12 hours 1 PM 90° 99° Mostly Cloudy 14%
RAIN
<.01 in		 0% Thunder
( 16% severe)		 SSE   13 58% 73°
High 94° SAN MARCOS, TX 78666 weather forecast Day 1, 15 hours 4 PM 93° 100° Mostly Cloudy SSE   14 49% 71°
Mostly Cloudy



 SAN MARCOS, TX 78666 weather forecast Day 1, 18 hours 7 PM 87° 93° Partly Cloudy 12%
RAIN
.1–.25 in		 0% Thunder
( 10% severe)		 SE   14 61% 72°
SAN MARCOS, TX 78666 weather forecast Day 1, 21 hours 10 PM 81° 86° Partly Cloudy SE   14 79% 74°
Wednesday
30 SEP 2026		 SAN MARCOS, TX 78666 weather forecast Day 2, 0 hours 1 AM 78° 80° Mostly Cloudy 32%
RAIN
.25–.5 in		 0% Thunder
( 10% severe)		 SSE   13 88% 74°
Low 73° SAN MARCOS, TX 78666 weather forecast Day 2, 3 hours 4 AM 76° 76° Mostly Cloudy SSE   13 94% 74°
High 97° SAN MARCOS, TX 78666 weather forecast Day 2, 6 hours 7 AM 75° 75° Mostly Cloudy 19%
RAIN
.01–.1 in		 0% Thunder
( 13% severe)		 SE   12 97% 74°

Mostly Cloudy

Chance of Rain

 SAN MARCOS, TX 78666 weather forecast Day 2, 9 hours 10 AM 82° 91° Mostly Cloudy SSE   14 88% 78°
SAN MARCOS, TX 78666 weather forecast Day 2, 12 hours 1 PM 91° 102° Mostly Cloudy 29%
RAIN
<.01 in		 0% Thunder
( 25% severe)		 S   16 60% 75°
SAN MARCOS, TX 78666 weather forecast Day 2, 15 hours 4 PM 93° 103° Mostly Cloudy SSE   17 54% 74°
SAN MARCOS, TX 78666 weather forecast Day 2, 18 hours 7 PM 87° 95° Partly Cloudy 18%
RAIN
.01–.1 in		 0% Thunder
( 20% severe)		 SSE   17 65% 74°
SAN MARCOS, TX 78666 weather forecast Day 2, 21 hours 10 PM 82° 89° Partly Cloudy SSE   15 82% 76°
Thursday
1 OCT 2026		 SAN MARCOS, TX 78666 weather forecast Day 3, 0 hours 1 AM 79° 83° Mostly Cloudy 66%
RAIN
1–2 in		 0% Thunder
( 18% severe)		 SSE   15 91% 76°
Low 73° SAN MARCOS, TX 78666 weather forecast Day 3, 3 hours 4 AM 77° 78° Mostly Cloudy SSE   14 94% 75°
High 91° SAN MARCOS, TX 78666 weather forecast Day 3, 6 hours 7 AM 75° 75° Mostly Cloudy 76%
RAIN
***		 0% Thunder
( 21% severe)		 SSE   13 100% 75°

Mostly Cloudy

Rain

 SAN MARCOS, TX 78666 weather forecast Day 3, 9 hours 10 AM 80° 87° Mostly Cloudy S   13 97% 79°
SAN MARCOS, TX 78666 weather forecast Day 3, 15 hours 1 PM 86° 98° Mostly Cloudy 92%
RAIN
***		 0% Thunder
( 54% severe)		 S   13 77% 78°
SAN MARCOS, TX 78666 weather forecast Day 3, 18 hours 4 PM 85° 96° Mostly Cloudy S   9 77% 77°
SAN MARCOS, TX 78666 weather forecast Day 3, 21 hours 7 PM 80° 86° Mostly Cloudy     SSE   7 91% 77°

SAN MARCOS, TX extended weather forecast
Friday
2 OCT 2026		 Saturday
3 OCT 2026		 Sunday
4 OCT 2026		 Monday
5 OCT 2026		 Tuesday
6 OCT 2026
Low 70° Low 69° Low 68° Low 66° Low 62°
High 82° High 83° High 85° High 83° High 84°
SAN MARCOS, TX 78666 weather forecast Day 4 SAN MARCOS, TX 78666 weather forecast Day 5 SAN MARCOS, TX 78666 weather forecast Day 6 SAN MARCOS, TX 78666 weather forecast Day 7 <!--SEARCHED_TOWN_NAME--> weather forecast Day 8
Overcast
88% Rain		 Overcast
64% Rain		 Overcast
44% Rain		 Overcast
21% Rain		 Mostly Cloudy
28% Rain
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