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

Planting zone for 78239 — San Antonio, TX

ZIP code 78239 (San Antonio, Bexar County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is February 21 and the first fall frost December 5.

Where ZIP 78239 is

Outlined: the ZIP code area · 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 frostFeb 21
First frostDec 5
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 Antonio, 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 Antonio, TX

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostFebruary 21median — 50% chance of a later frost
Safe for tender plantsMarch 14only 10% chance of frost after
First fall frostDecember 5median — 10% chance by Nov 16
Growing season289 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 26 and returns around December 19.

From the NOAA station Randolph AFB, TX — 6 miles away, elevation 761 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 78239

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 10 – Jan 24
SpinachSow outdoors · Jan 10 – Jan 31
Broccoli, cabbageStart indoors · Dec 13 – Dec 27
Broccoli, cabbageTransplant · Jan 31 – Feb 14
Onion setsPlant outdoors · Jan 24 – Feb 7
PotatoesPlant outdoors · Jan 31 – Feb 14
LettuceSow outdoors · Jan 24 – Feb 7
Carrots, beetsSow outdoors · Jan 31 – Feb 14
TomatoesStart indoors · Dec 27 – Jan 10
TomatoesTransplant · Feb 28 – Mar 14
Peppers, eggplantStart indoors · Dec 13 – Dec 27
Peppers, eggplantTransplant · Mar 7 – Mar 21
BeansSow outdoors · Feb 28 – Mar 14
Sweet cornSow outdoors · Feb 28 – Mar 14
Cucumbers, squashSow outdoors · Feb 28 – Mar 14
Fall lettuce, spinachSow outdoors · Oct 10 – Oct 24
GarlicPlant cloves · Nov 21 – Dec 26
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 21) and first fall frost (Dec 5) 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 78239 came on Jan 20 — 5 days earlier than the 1991–2020 average (Jan 25).

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 Antonio, TX.

Soil in San Antonio, TX

The soil mapped at the center of ZIP 78239 is Houston Black — gravelly clay, moderately well drained.

TextureGravelly clayholds water and nutrients; slow to drain and warm up
pH7.9alkaline; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter3%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classprime farmlandUSDA classification

Map unit: Houston Black gravelly clay, 3 to 5 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 78239; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in San Antonio, TX

Summer high96 °Faverage high, July
Winter low41 °Faverage low, January
Hot days133days a year at 90 °F or more
Freezing nights12nights a year at 32 °F or less
Growing degree days7,163base 50 °F — the season’s usable heat
Longest day14 h 02 mindaylight on June 21
Shortest day10 h 15 mindaylight on December 21
Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb
Precipitation32.7 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 63 °F, low 41 °F 63°41° JanFebruary: average high 68 °F, low 45 °F 68°45° FebMarch: average high 73 °F, low 51 °F 73°51° MarApril: average high 80 °F, low 58 °F 80°58° AprMay: average high 87 °F, low 66 °F 87°66° MayJune: average high 92 °F, low 71 °F 92°71° JunJuly: average high 96 °F, low 73 °F 96°73° JulAugust: average high 96 °F, low 73 °F 96°73° AugSeptember: average high 90 °F, low 68 °F 90°68° SepOctober: average high 84 °F, low 59 °F 84°59° OctNovember: average high 72 °F, low 49 °F 72°49° NovDecember: average high 64 °F, low 42 °F 64°42° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 1.94 in precipitation 1.9 JanFebruary: 1.86 in precipitation 1.9 FebMarch: 2.55 in precipitation 2.5 MarApril: 2.33 in precipitation 2.3 AprMay: 4.12 in precipitation 4.1 MayJune: 3.44 in precipitation 3.4 JunJuly: 2.27 in precipitation 2.3 JulAugust: 2.37 in precipitation 2.4 AugSeptember: 3.36 in precipitation 3.4 SepOctober: 3.69 in precipitation 3.7 OctNovember: 2.52 in precipitation 2.5 NovDecember: 2.24 in precipitation 2.2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Randolph AFB, TX (6 mi away); precipitation: Windcrest 1.7 E, TX (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9a.

782189a
San Antonio, TX · 3 mi
782339a
San Antonio, TX · 3 mi
782449a
San Antonio, TX · 3 mi
782179a
San Antonio, TX · 4 mi
781489a
Universal City, TX · 4 mi
781099a
Converse, TX · 5 mi
782479a
San Antonio, TX · 5 mi
782199a
San Antonio, TX · 5 mi

All 82 ZIP codes in San Antonio → · Texas planting zones →

Questions about 78239

What planting zone is ZIP code 78239?

ZIP code 78239 (San Antonio, 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 Antonio, TX?

The median last spring frost (32 °F) near 78239 is February 21; after March 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Randolph AFB station.

When is the first frost in San Antonio, TX?

The median first fall frost near 78239 is December 5, giving a median frost-free growing season of 289 days.

When should I plant tomatoes in 78239?

Start tomato seeds indoors around Dec 27 – Jan 10 and set transplants outside around Feb 28 – Mar 14, one to three weeks after the median last frost.

How much rain and snow does 78239 get?

About 32.7 inches of precipitation a year (NOAA 1991–2020 normals, Windcrest 1.7 E station).

How hot do summers get in San Antonio, TX?

The average high peaks at 96 °F in July, with about 133 days a year at 90 °F or more.

What kind of soil does 78239 have?

The USDA soil survey maps Houston Black at the center of ZIP 78239: gravelly clay, moderately well drained, pH about 7.9 (alkaline).

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

Spring leaf-out near 78239 came on Jan 20 in 2026, 5 days earlier than the 1991–2020 average (Jan 25), according to the USA National Phenology Network Spring Index.

What kind of onions grow in San Antonio, TX?

Short-day onions: the longest day near 78239 is 14 h 02 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.

Did the zone for 78239 change?

Yes. The 2012 USDA map put 78239 in zone 8b; the 2023 map puts it in zone 9a. The newer map uses 1991–2020 data and more weather stations.