Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 78667 — San Marcos, TX

ZIP code 78667 (San Marcos, Hays County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is March 17 and the first fall frost November 13.

Where ZIP 78667 is

tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone9a20 to 25 °F

Coldest night−6.7 to −3.9 °C

Last frostMar 17

First frostNov 13

2012 zone8b

Was 8b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 9a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for San Marcos, TX…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in San Marcos, TX

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMarch 17median — 50% chance of a later frost

Safe for tender plantsApril 7only 10% chance of frost after

First fall frostNovember 13median — 10% chance by Oct 29

Growing season242 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 4 and returns around November 26.

From the NOAA station Dripping Springs 6 E, TX — 11 miles away, elevation 1,083 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 78667

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 3 – Feb 17

SpinachSow outdoors · Feb 3 – Feb 24

Broccoli, cabbageStart indoors · Jan 6 – Jan 20

Broccoli, cabbageTransplant · Feb 24 – Mar 10

Onion setsPlant outdoors · Feb 17 – Mar 3

PotatoesPlant outdoors · Feb 24 – Mar 10

LettuceSow outdoors · Feb 17 – Mar 3

Carrots, beetsSow outdoors · Feb 24 – Mar 10

TomatoesStart indoors · Jan 20 – Feb 3

TomatoesTransplant · Mar 24 – Apr 7

Peppers, eggplantStart indoors · Jan 6 – Jan 20

Peppers, eggplantTransplant · Mar 31 – Apr 14

BeansSow outdoors · Mar 24 – Apr 7

Sweet cornSow outdoors · Mar 24 – Apr 7

Cucumbers, squashSow outdoors · Mar 24 – Apr 7

Fall lettuce, spinachSow outdoors · Sep 18 – Oct 2

GarlicPlant cloves · Oct 30 – Dec 4

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 17) and first fall frost (Nov 13) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 78667 came on Jan 30 — 3 days later than the 1991–2020 average (Jan 27).

average
Jan 272026
Jan 30

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 9a in Texas

640 plants native to the lower 48 states, recorded in Texas, and rated by the USDA to survive 20 °F or colder — the bottom of zone 9a. Each links to its USDA PLANTS profile.

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in San Marcos, TX.

Soil in San Marcos, TX

The soil mapped at the center of ZIP 78667 is Comfort — very stony clay, well drained.

TextureVery stony clayholds water and nutrients; slow to drain and warm up

pH7.5slightly alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter6%high

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Comfort-Rock outcrop complex, 1 to 8 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 78667; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in San Marcos, TX

Summer high95 °Faverage high, August

Winter low39 °Faverage low, January

Hot days106days a year at 90 °F or more

Freezing nights29nights a year at 32 °F or less

Growing degree days6,729base 50 °F — the season’s usable heat

Longest day14 h 05 mindaylight on June 21

Shortest day10 h 12 mindaylight on December 21

Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb

Precipitation37.3 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Dripping Springs 6 E, TX (11 mi away); precipitation: Mountain City 6.7 Wnw, TX (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

3 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

San Marcos, TX · 12 mi

All 2 ZIP codes in San Marcos → · Texas planting zones →

Questions about 78667

What planting zone is ZIP code 78667?

ZIP code 78667 (San Marcos, TX) is in USDA hardiness zone 9a on the 2023 map: the coldest night of an average winter reaches 20 to 25 °F (−6.7 to −3.9 °C).

When is the last frost in San Marcos, TX?

The median last spring frost (32 °F) near 78667 is March 17; after April 7 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Dripping Springs 6 E station.

When is the first frost in San Marcos, TX?

The median first fall frost near 78667 is November 13, giving a median frost-free growing season of 242 days.

When should I plant tomatoes in 78667?

Start tomato seeds indoors around Jan 20 – Feb 3 and set transplants outside around Mar 24 – Apr 7, one to three weeks after the median last frost.

How much rain and snow does 78667 get?

About 37.3 inches of precipitation a year (NOAA 1991–2020 normals, Mountain City 6.7 Wnw station).

How hot do summers get in San Marcos, TX?

The average high peaks at 95 °F in August, with about 106 days a year at 90 °F or more.

What kind of soil does 78667 have?

The USDA soil survey maps Comfort at the center of ZIP 78667: very stony clay, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in San Marcos, TX in 2026?

Spring leaf-out near 78667 came on Jan 30 in 2026, 3 days later than the 1991–2020 average (Jan 27), according to the USA National Phenology Network Spring Index.

What kind of onions grow in San Marcos, TX?

Short-day onions: the longest day near 78667 is 14 h 05 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.

Did the zone for 78667 change?

Yes. The 2012 USDA map put 78667 in zone 8b; the 2023 map puts it in zone 9a. The newer map uses 1991–2020 data and more weather stations.