Skip to content
WeatherSignal logoWeatherSignal
Sign up

Weather for 78666 — San Marcos, TX

Conditions and forecast for the exact centre of ZIP code 78666 (29.875, -97.940), not a nearby airport.

68°

Overcast

Feels like:
68°
Humidity:
83%
Wind:
19 mph
Dew point:
62°

Source updated: 11:52:59 AM · WeatherSignal checked: 11:52:59 AM

Source: Open-Meteo (national weather-service models)

Next 12 hours in 78666

12 PM

66°

0%

1 PM

65°

0%

2 PM

64°

0%

3 PM

64°

0%

4 PM

64°

0%

5 PM

67°

0%

6 PM

71°

0%

7 PM

72°

0%

8 PM

72°

0%

9 PM

71°

0%

10 PM

69°

0%

11 PM

67°

0%

7 day forecast for 78666

  • Today

    72° / 64°

    0% rain · 24 mph wind

  • Saturday, Oct 17

    68° / 53°

    0% rain · 20 mph wind

  • Sunday, Oct 18

    72° / 51°

    0% rain · 9 mph wind

  • Monday, Oct 19

    73° / 52°

    0% rain · 5 mph wind

  • Tuesday, Oct 20

    79° / 58°

    0% rain · 6 mph wind

  • Wednesday, Oct 21

    78° / 59°

    0% rain · 5 mph wind

  • Thursday, Oct 22

    80° / 57°

    0% rain · 3 mph wind

About ZIP code 78666

78666 covers San Marcos in Texas. Forecasts on this page are generated for the coordinates at the centre of the ZIP code, so small differences from a nearby city forecast are expected and usually correct.

Closest cities with full forecast pages: Austin (29 mi), San Antonio (45 mi), Round Rock (46 mi), Killeen (87 mi).

Nearby ZIP codes

Severe weather warnings are issued by the National Weather Service for counties and polygons that may not line up with ZIP code boundaries. Always follow official warnings for your exact address.

Planning your week in San Marcos 78666, Texas

  • The warmest afternoon ahead is Thursday, reaching about 80°F.
  • The coldest night ahead dips to about 51°F.
  • This is a dry stretch — most days show rain chances under 20%, good for outdoor plans.
  • The breeziest day looks like today, with sustained wind near 24 mph.
  • UV reaches 7 on the sunniest day — sunscreen is worth it if you will be outside around midday.

Common questions about San Marcos 78666, Texas weather

How accurate is the San Marcos 78666, Texas forecast?
The next 48 hours are usually reliable on temperature and sky cover, with timing that can shift by an hour or two. Days three and four are dependable for the overall pattern. Beyond that, treat the numbers as a planning direction rather than a promise — we label confidence on every day so you can judge for yourself.
What is the best day this week in San Marcos 78666, Texas?
No day in the current outlook has a rain chance above 40%, so conditions look favorable for outdoor plans across the week.
Where does this forecast come from?
Forecast values come from national weather model data, and official warnings come from the National Weather Service. We show the source and the last-updated time on every page, and we never invent a number the source did not publish — missing measurements are hidden, not guessed.
How often is this page updated?
The forecast refreshes whenever the source model publishes new data, typically several times a day. The freshness note near the top of the page shows exactly when the numbers you are looking at were issued.

More weather for San Marcos 78666, Texas

Weather in nearby cities

Weather Signal is free for everyone. Donations keep it running, and a portion goes to our Community Relief program, which helps a household with an essential bill at the end of the month. Members can enter for free without donating.

Donate