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
12:56 PM CDT MAY 21, 2026
Broken Clouds
77°F
Feels Like: 79°F
Dewpoint: 70°F
Rel. Hum.: 79%
Visibility: 9 miles
Wind: Calm
Pressure: 29.97 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
2025 Hurricanes

SAN MARCOS, TX 78666
Weather Forecast

 Snowfall Forecast pages
Snow Depth pages
TODAY
Mostly cloudy with a chance of showers and thunderstorms. Highs around 80. East winds around 5 mph, becoming south this afternoon. Chance of rain 50 percent.
TONIGHT
Partly cloudy with a chance of showers and thunderstorms in the evening, then mostly cloudy with a slight chance of showers and thunderstorms after midnight. Lows in the upper 60s. South winds around 5 mph. Chance of rain 30 percent.
FRIDAY
Partly cloudy. Highs in the upper 80s. South winds around 5 mph.
FRIDAY NIGHT
Partly cloudy with a chance of showers and thunderstorms in the evening, then mostly cloudy with a slight chance of showers and thunderstorms after midnight. Lows around 70. South winds 5 to 10 mph. Chance of rain 40 percent.
SATURDAY
A chance of thunderstorms. Showers. Highs in the lower 80s. Temperature falling into the mid 70s in the afternoon. South winds around 5 mph. Chance of rain 90 percent.
SATURDAY NIGHT
A chance of thunderstorms. Showers. Lows in the upper 60s. Chance of rain 80 percent.
SUNDAY
Mostly cloudy with a chance of showers and thunderstorms in the morning, then partly cloudy with showers and thunderstorms likely in the afternoon. Highs in the lower 80s. Chance of rain 70 percent.
SUNDAY NIGHT
Partly cloudy. A chance of showers and thunderstorms, mainly in the evening. Lows in the upper 60s. Chance of rain 40 percent.
MEMORIAL DAY
Mostly cloudy in the morning, then partly cloudy with a chance of showers and thunderstorms in the afternoon. Highs in the mid 80s. Chance of rain 30 percent.
MONDAY NIGHT
Mostly clear in the evening, then becoming partly cloudy. A slight chance of showers and thunderstorms. Lows in the upper 60s.
TUESDAY
Mostly cloudy with a slight chance of showers and thunderstorms in the morning, then partly cloudy with a chance of showers and thunderstorms in the afternoon. Highs in the mid 80s. Chance of rain 40 percent.
TUESDAY NIGHT
Partly cloudy in the evening, then becoming mostly cloudy. A chance of showers and thunderstorms. Lows in the lower 70s. Chance of rain 50 percent.
WEDNESDAY
Mostly cloudy with a chance of thunderstorms. A chance of showers in the morning, then showers likely in the afternoon. Highs in the mid 80s. Chance of rain 70 percent.

  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  5/21/2026
Thursday
21 MAY 2026		 SAN MARCOS, TX 78666 weather forecast Day 1, 12 hours 1 PM 76° 77° Mostly Cloudy 33%
RAIN
.1–.25 in		 0% Thunder
( 46% severe)		 SSE   7 82% 70°
High 79° SAN MARCOS, TX 78666 weather forecast Day 1, 15 hours 4 PM 78° 80° Mostly Cloudy SSE   7 76% 70°
Mostly Cloudy

Chance of Rain

 SAN MARCOS, TX 78666 weather forecast Day 1, 18 hours 7 PM 76° 77° Mostly Cloudy 25%
RAIN
.25–.5 in		 0% Thunder
( 26% severe)		 SE   7 79% 69°
SAN MARCOS, TX 78666 weather forecast Day 1, 21 hours 10 PM 71° 71° Mostly Cloudy SE   2 93% 69°
Friday
22 MAY 2026		 SAN MARCOS, TX 78666 weather forecast Day 2, 0 hours 1 AM 70° 70° Mostly Cloudy 17%
RAIN
.1–.25 in		 0% Thunder
( 17% severe)		 W   2 93% 68°
Low 68° SAN MARCOS, TX 78666 weather forecast Day 2, 3 hours 4 AM 70° 70° Mostly Cloudy SE   3 93% 68°
High 87° SAN MARCOS, TX 78666 weather forecast Day 2, 6 hours 7 AM 69° 69° Partly Cloudy 15%
RAIN
.25–.5 in		 0% Thunder
( 22% severe)		   CALM 97% 68°

Partly Cloudy



 SAN MARCOS, TX 78666 weather forecast Day 2, 9 hours 10 AM 75° 75° Partly Cloudy SE   6 87% 71°
SAN MARCOS, TX 78666 weather forecast Day 2, 12 hours 1 PM 82° 86° Partly Cloudy 17%
RAIN
<.01 in		 0% Thunder
( 25% severe)		 S   7 69% 71°
SAN MARCOS, TX 78666 weather forecast Day 2, 15 hours 4 PM 85° 90° Partly Cloudy S   8 63% 71°
SAN MARCOS, TX 78666 weather forecast Day 2, 18 hours 7 PM 81° 84° Partly Cloudy 12%
RAIN
<.01 in		 0% Thunder
( 21% severe)		 SE   9 69% 70°
SAN MARCOS, TX 78666 weather forecast Day 2, 21 hours 10 PM 74° 74° Partly Cloudy SSE   7 87% 70°
Saturday
23 MAY 2026		 SAN MARCOS, TX 78666 weather forecast Day 3, 0 hours 1 AM 73° 73° Partly Cloudy 24%
RAIN
.5–1 in		 0% Thunder
( 24% severe)		 S   6 90% 70°
Low 71° SAN MARCOS, TX 78666 weather forecast Day 3, 3 hours 4 AM 72° 72° Mostly Cloudy SSE   5 93% 70°
High 84° SAN MARCOS, TX 78666 weather forecast Day 3, 6 hours 7 AM 72° 72° Mostly Cloudy 55%
RAIN
***		 0% Thunder
( 35% severe)		 SE   5 93% 70°

Mostly Cloudy

Rain Likely

 SAN MARCOS, TX 78666 weather forecast Day 3, 9 hours 10 AM 75° 75° Mostly Cloudy SSE   7 90% 72°
SAN MARCOS, TX 78666 weather forecast Day 3, 15 hours 1 PM 79° 82° Mostly Cloudy 79%
RAIN
***		 0% Thunder
( 52% severe)		 SSW   9 79% 72°
SAN MARCOS, TX 78666 weather forecast Day 3, 18 hours 4 PM 78° 80° Mostly Cloudy SE   9 82% 72°
SAN MARCOS, TX 78666 weather forecast Day 3, 21 hours 7 PM 74° 74° Mostly Cloudy     SE   8 87% 70°

SAN MARCOS, TX extended weather forecast
Sunday
24 MAY 2026		 Monday
25 MAY 2026		 Tuesday
26 MAY 2026		 Wednesday
27 MAY 2026		 Thursday
28 MAY 2026
Low 64° Low 64° Low 65° Low 66° Low 68°
High 87° High 86° High 90° High 87° High 88°
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
36% Rain		 Mostly Cloudy
63% Rain		 Overcast
50% Rain		 Overcast
53% Rain		 Overcast
34% Rain
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