ZIP code · San Marcos · Texas · United States
ZIP code 78666 — San Marcos
ZIP code 78666 serves San Marcos, Texas.
- Postal code
- 78666Single source Value from one source, not cross-checked.
- City
- San Marcos
- County
- Hays FIPS 48209
- State
- Texas
- Country
- United States
- Coordinates
- 29.8754, -97.9404 — precision precise (locality)
View on OpenStreetMap - Population
- 87,775 (ZCTA, ACS 5-year)
- Population density
- 456 / sq mi
- Land area
- 192.4 sq mi (498.3 km²) (ZCTA, ACS 5-year)
- Median household income
- $55,478
- Per-capita income
- $28,813
- Median age
- 27
- Households
- 33,836
- Housing units
- 36,354
- Median home value
- $271,900
- Median gross rent
- $1,294 / month
- Congressional districts
- TX-21 (also TX-35, TX-15, TX-27) (119th Congress)
- USDA hardiness zone
- 9a (20 to 25 °F)Planting / growing zone from the 2023 USDA Plant Hardiness Zone Map: average annual extreme minimum temperature, 1991–2020.
- Time zone
- America/Chicago (UTC−6 / UTC−5 DST)
Tools: compare 78666 with another ZIP · ZIPs within 25 miles · distance from 78666
Map of ZIP code 78666
Climate — monthly normals
Warmest month Aug (avg high 97°F), coldest Jan (avg low 39°F).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 62 | 67 | 73 | 80 | 86 | 92 | 96 | 97 | 91 | 82 | 72 | 64 |
| Avg low °F | 39 | 42 | 50 | 56 | 65 | 72 | 73 | 74 | 69 | 58 | 48 | 41 |
| Precip in | 2.4 | 1.7 | 2.8 | 3.2 | 4.5 | 3.6 | 2.2 | 2.6 | 4.0 | 4.4 | 2.7 | 2.4 |
NOAA 1991–2020 climate normals from the nearest station: SAN MARCOS (0.7 mi) · NOAA NCEI
Places in ZIP 78666
- 21 schools
- 3 colleges & universities
- 3 hospitals & clinics
- 8 doctors & dentists
- 7 pharmacies
- 3 supermarkets
- 151 restaurants & cafés
- 19 bars & pubs
- 42 parks
- 11 playgrounds
- 16 gyms & sports centres
- 2 libraries
- 2 post offices
- 34 places of worship
- 12 banks
- 36 gas stations
- 4 EV charging stations
- 5 police & fire stations
Places mapped inside this ZIP’s ZCTA area in OpenStreetMap. OSM is community-maintained: counts reflect what has been mapped, and completeness varies by area — treat them as at-least figures. © OpenStreetMap contributors (ODbL) · Methodology
About this page
US ZIP codes have five digits. They are postal routing areas, not administrative boundaries: a ZIP can span more than one city or county, and the city shown is the primary USPS name for that code.
GeoNames · U.S. Census Bureau (ACS) · U.S. Census Bureau · NOAA NCEI · usda-phzm. Data generated on 2026-08-21. Methodology · Report an error on this page