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

Planting zone for San Marcos, TX

San Marcos, TX is in USDA zone 9a across its 2 ZIP codes. The median last spring frost is February 28 and the first fall frost November 29.

San Marcos on the zone map

Outlined: its 1 ZIP code areas · 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
ZIP codes2
Last frostFeb 28
First frostNov 29
Growing season273 days

9a 2 ZIPs

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 frostFebruary 28median — 50% chance of a later frost
Safe for tender plantsMarch 21only 10% chance of frost after
First fall frostNovember 29median — 10% chance by Nov 8
Growing season273 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 13 and returns around December 15.

From the NOAA station San Marcos, TX, elevation 666 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 San Marcos

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 17 – Jan 31
SpinachSow outdoors · Jan 17 – Feb 7
Broccoli, cabbageStart indoors · Dec 20 – Jan 3
Broccoli, cabbageTransplant · Feb 7 – Feb 21
Onion setsPlant outdoors · Jan 31 – Feb 14
PotatoesPlant outdoors · Feb 7 – Feb 21
LettuceSow outdoors · Jan 31 – Feb 14
Carrots, beetsSow outdoors · Feb 7 – Feb 21
TomatoesStart indoors · Jan 3 – Jan 17
TomatoesTransplant · Mar 7 – Mar 21
Peppers, eggplantStart indoors · Dec 20 – Jan 3
Peppers, eggplantTransplant · Mar 14 – Mar 28
BeansSow outdoors · Mar 7 – Mar 21
Sweet cornSow outdoors · Mar 7 – Mar 21
Cucumbers, squashSow outdoors · Mar 7 – Mar 21
Fall lettuce, spinachSow outdoors · Oct 4 – Oct 18
GarlicPlant cloves · Nov 15 – Dec 20
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 28) and first fall frost (Nov 29) 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).

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.

Trees 72

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °FArizona cypress50 ft · blooms spring · low shade tolerance · to −23 °FArizona walnut50 ft · blooms late spring · high shade tolerance · to −33 °F

Shrubs 141

alderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °Faloe yucca15 ft · blooms early summer · medium shade tolerance · to −1 °FAmerican beautyberry6 ft · blooms early summer · medium shade tolerance · to −8 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °FAmerican hornbeam30 ft · blooms mid spring · low shade tolerance · to −34 °FAmerican snowbell10 ft · blooms spring · medium shade tolerance · to −16 °F

Wildflowers & perennials 208

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican century plant6 ft · blooms indeterminate · high shade tolerance · to 12 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °F

Grasses 196

alkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °FArizona cottontop4 ft · blooms late summer · high shade tolerance · to −13 °FArizona fescue2 ft · blooms late spring · high shade tolerance · to −23 °FArizona threeawn2 ft · blooms mid summer · high shade tolerance · to −3 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °F

Vines 14

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fcatbird grape30 ft · blooms late spring · medium shade tolerance · to −13 °Fcupseed30 ft · blooms late spring · low shade tolerance · to −3 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °F

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 04 mindaylight on June 21
Shortest day10 h 13 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

30°40°50°60°70°80°90°100°110°32 °FJanuary: average high 60 °F, low 39 °F 60°39° JanFebruary: average high 65 °F, low 43 °F 65°43° FebMarch: average high 72 °F, low 49 °F 72°49° MarApril: average high 79 °F, low 56 °F 79°56° AprMay: average high 85 °F, low 64 °F 85°64° MayJune: average high 91 °F, low 70 °F 91°70° JunJuly: average high 94 °F, low 72 °F 94°72° JulAugust: average high 95 °F, low 72 °F 95°72° AugSeptember: average high 89 °F, low 66 °F 89°66° SepOctober: average high 80 °F, low 58 °F 80°58° OctNovember: average high 69 °F, low 48 °F 69°48° NovDecember: average high 61 °F, low 41 °F 61°41° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 2.56 in precipitation 2.6 JanFebruary: 2.00 in precipitation 2.0 FebMarch: 2.82 in precipitation 2.8 MarApril: 2.50 in precipitation 2.5 AprMay: 4.99 in precipitation 5.0 MayJune: 3.51 in precipitation 3.5 JunJuly: 2.45 in precipitation 2.5 JulAugust: 2.56 in precipitation 2.6 AugSeptember: 3.80 in precipitation 3.8 SepOctober: 4.44 in precipitation 4.4 OctNovember: 2.84 in precipitation 2.8 NovDecember: 2.78 in precipitation 2.8 Dec

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.

ZIP codes in San Marcos

786669a
20 to 25 °F
786679a
20 to 25 °F

Texas planting zones →

Questions about San Marcos

What planting zone is San Marcos, TX?

San Marcos, TX is in USDA hardiness zone 9a on the 2023 map (9a: 20 to 25 °F).

When is the last frost in San Marcos, TX?

The median last spring frost is February 28 and the median first fall frost is November 29 (NOAA 1991–2020 normals, San Marcos station).

When can I plant a garden in San Marcos, TX?

Cool-season crops like peas and spinach go in around Jan 17 – Feb 7; tomatoes, peppers, beans and squash after about Mar 7, once frost risk has passed.

What kind of onions grow in San Marcos, TX?

Short-day onions: the longest day is 14 h 04 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.

How much rain and snow does San Marcos, TX get?

About 37.3 inches of precipitation a year (NOAA 1991–2020 normals).