SAN MARCOS, TX 78666 Weather Forecast & Current Conditions

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SAN MARCOS, TX
Current Weather

3:56 AM CDT SEP 9, 2026
Clear
79°F
Feels Like: 83°F
Dewpoint: 75°F
Rel. Hum.: 88%
Visibility: 10 miles
Wind: Calm
Pressure: 30.09 inches
Last 72 hours

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SAN MARCOS, TX 78666
Weather Forecast

Snowfall Forecast pages
Snow Depth pages
TODAY
Partly cloudy. Highs in the upper 90s. Southeast winds 5 to 10 mph. Highest heat index readings up to 105.
TONIGHT
Partly cloudy. Lows in the mid 70s. South winds 5 to 10 mph.
THURSDAY
Partly cloudy in the morning, then becoming mostly sunny. Highs in the upper 90s. South winds around 5 mph.
THURSDAY NIGHT
Mostly clear in the evening, then becoming partly cloudy. Lows in the mid 70s. South winds around 5 mph.
FRIDAY
Partly cloudy. Highs in the upper 90s. South winds 5 to 10 mph. Highest heat index readings up to 107.
FRIDAY NIGHT
Partly cloudy. Lows in the mid 70s.
SATURDAY AND SATURDAY NIGHT
Mostly clear. Highs in the upper 90s. Lows in the mid 70s. Highest heat index readings up to 110.
SUNDAY THROUGH MONDAY
Partly cloudy. Highs in the upper 90s. Lows in the mid 70s. Highest heat index readings up to 110.
MONDAY NIGHT
Mostly clear. Lows in the mid 70s.
TUESDAY
Mostly cloudy in the morning, then clearing. Highs in the upper 90s. Highest heat index readings up to 110.

Visible Weather Satellite
SAN MARCOS, TX 78666
Infrared Weather Satellite
SAN MARCOS, TX 78666
NEXRAD Weather Radar
SAN MARCOS, TX 78666

SAN MARCOS, TX 3 hourly weather forecast

weather forecast created  8:00 PM EDT  9/ 8/2026
Wednesday
9 SEP 2026
SAN MARCOS, TX 78666 weather forecast Day 1, 0 hours 1 AM 81° 86° Partly Cloudy 1%

0% Thunder
( 10% severe)
S   7 79% 74°
Low 75° SAN MARCOS, TX 78666 weather forecast Day 1, 3 hours 4 AM 78° 81° Partly Cloudy S   3 91% 75°
High 99° SAN MARCOS, TX 78666 weather forecast Day 1, 6 hours 7 AM 76° 75° Mostly Cloudy 2%

0% Thunder
( 11% severe)
  CALM 97% 75°

Mostly Cloudy



SAN MARCOS, TX 78666 weather forecast Day 1, 9 hours 10 AM 84° 94° Partly Cloudy S   5 80% 77°
SAN MARCOS, TX 78666 weather forecast Day 1, 12 hours 1 PM 93° 102° Partly Cloudy 8%

0% Thunder
( 33% severe)
SSE   6 52% 73°
SAN MARCOS, TX 78666 weather forecast Day 1, 15 hours 4 PM 95° 103° Mostly Cloudy SE   7 46% 71°
SAN MARCOS, TX 78666 weather forecast Day 1, 18 hours 7 PM 90° 96° Mostly Cloudy 4%

0% Thunder
( 14% severe)
SE   12 54% 71°
SAN MARCOS, TX 78666 weather forecast Day 1, 21 hours 10 PM 83° 90° Partly Cloudy SSE   8 74% 74°
Thursday
10 SEP 2026
SAN MARCOS, TX 78666 weather forecast Day 2, 0 hours 1 AM 80° 85° Partly Cloudy 6%

0% Thunder
( 11% severe)
S   5 82% 74°
Low 74° SAN MARCOS, TX 78666 weather forecast Day 2, 3 hours 4 AM 77° 78° Partly Cloudy S   3 90% 74°
High 98° SAN MARCOS, TX 78666 weather forecast Day 2, 6 hours 7 AM 75° 75° Partly Cloudy 1%

0% Thunder
( 5% severe)
  CALM 97% 74°

Partly Cloudy



SAN MARCOS, TX 78666 weather forecast Day 2, 9 hours 10 AM 84° 93° Partly Cloudy S   2 77% 76°
SAN MARCOS, TX 78666 weather forecast Day 2, 12 hours 1 PM 93° 101° Clear 7%

0% Thunder
( 30% severe)
SSE   5 51% 72°
SAN MARCOS, TX 78666 weather forecast Day 2, 15 hours 4 PM 95° 102° Partly Cloudy SSE   5 45% 70°
SAN MARCOS, TX 78666 weather forecast Day 2, 18 hours 7 PM 92° 97° Partly Cloudy 7%

0% Thunder
( 17% severe)
SE   8 47% 69°
SAN MARCOS, TX 78666 weather forecast Day 2, 21 hours 10 PM 83° 89° Partly Cloudy SSE   8 72% 73°

SAN MARCOS, TX extended weather forecast

Friday
11 SEP 2026
Saturday
12 SEP 2026
Sunday
13 SEP 2026
Monday
14 SEP 2026
Tuesday
15 SEP 2026
Low 75° Low 74° Low 76° Low 76° Low 75°
High 96° High 92° High 95° High 96° High 96°
SAN MARCOS, TX 78666 weather forecast Day 3 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
Overcast
46% Rain
Overcast
39% Rain
Overcast
32% Rain
Partly Cloudy
12% Rain
Mostly Cloudy
18% Rain
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