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

Planting zone for 78221 — San Antonio, TX

ZIP code 78221 (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 20 and the first fall frost December 3.

Where ZIP 78221 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 20
First frostDec 3
2012 zone9a

Same zone as on the 2012 map. 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 20median — 50% chance of a later frost
Safe for tender plantsMarch 13only 10% chance of frost after
First fall frostDecember 3median — 10% chance by Nov 12
Growing season291 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 30 and returns around December 23.

From the NOAA station San Antonio Stinson Airport, TX — 3 miles away, elevation 571 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 78221

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 9 – Jan 23
SpinachSow outdoors · Jan 9 – Jan 30
Broccoli, cabbageStart indoors · Dec 12 – Dec 26
Broccoli, cabbageTransplant · Jan 30 – Feb 13
Onion setsPlant outdoors · Jan 23 – Feb 6
PotatoesPlant outdoors · Jan 30 – Feb 13
LettuceSow outdoors · Jan 23 – Feb 6
Carrots, beetsSow outdoors · Jan 30 – Feb 13
TomatoesStart indoors · Dec 26 – Jan 9
TomatoesTransplant · Feb 27 – Mar 13
Peppers, eggplantStart indoors · Dec 12 – Dec 26
Peppers, eggplantTransplant · Mar 6 – Mar 20
BeansSow outdoors · Feb 27 – Mar 13
Sweet cornSow outdoors · Feb 27 – Mar 13
Cucumbers, squashSow outdoors · Feb 27 – Mar 13
Fall lettuce, spinachSow outdoors · Oct 8 – Oct 22
GarlicPlant cloves · Nov 19 – Dec 24
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 20) and first fall frost (Dec 3) 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 78221 came on Jan 15 — 9 days earlier than the 1991–2020 average (Jan 24).

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 78221 is Loire — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH8.2alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.55%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Loire clay loam, 0 to 2 percent slopes, occasionally flooded.

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 78221; 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 high98 °Faverage high, August
Winter low42 °Faverage low, January
Hot days134days a year at 90 °F or more
Freezing nights14nights a year at 32 °F or less
Growing degree days7,858base 50 °F — the season’s usable heat
Longest day14 h 01 mindaylight on June 21
Shortest day10 h 16 mindaylight on December 21
Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb
Precipitation29.7 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 65 °F, low 42 °F 65°42° JanFebruary: average high 69 °F, low 47 °F 69°47° FebMarch: average high 75 °F, low 54 °F 75°54° MarApril: average high 82 °F, low 60 °F 82°60° AprMay: average high 88 °F, low 68 °F 88°68° MayJune: average high 94 °F, low 74 °F 94°74° JunJuly: average high 96 °F, low 75 °F 96°75° JulAugust: average high 98 °F, low 76 °F 98°76° AugSeptember: average high 91 °F, low 71 °F 91°71° SepOctober: average high 84 °F, low 62 °F 84°62° OctNovember: average high 73 °F, low 51 °F 73°51° NovDecember: average high 66 °F, low 44 °F 66°44° Dec

Precipitation by month inches

0″1″2″3″4″January: 1.79 in precipitation 1.8 JanFebruary: 1.56 in precipitation 1.6 FebMarch: 2.43 in precipitation 2.4 MarApril: 2.34 in precipitation 2.3 AprMay: 3.88 in precipitation 3.9 MayJune: 3.17 in precipitation 3.2 JunJuly: 1.78 in precipitation 1.8 JulAugust: 2.50 in precipitation 2.5 AugSeptember: 3.15 in precipitation 3.1 SepOctober: 3.02 in precipitation 3.0 OctNovember: 2.01 in precipitation 2.0 NovDecember: 2.10 in precipitation 2.1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: San Antonio Stinson Airport, TX (3 mi away); precipitation: San Antonio Stinson Airport, TX (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9a.

782149a
San Antonio, TX · 4 mi
782249a
San Antonio, TX · 4 mi
782359a
San Antonio, TX · 4 mi
782239a
San Antonio, TX · 6 mi
782119a
San Antonio, TX · 6 mi
782259a
San Antonio, TX · 7 mi
782109a
San Antonio, TX · 7 mi
782649a
San Antonio, TX · 7 mi

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

Questions about 78221

What planting zone is ZIP code 78221?

ZIP code 78221 (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 78221 is February 20; after March 13 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, San Antonio Stinson Airport station.

When is the first frost in San Antonio, TX?

The median first fall frost near 78221 is December 3, giving a median frost-free growing season of 291 days.

When should I plant tomatoes in 78221?

Start tomato seeds indoors around Dec 26 – Jan 9 and set transplants outside around Feb 27 – Mar 13, one to three weeks after the median last frost.

How much rain and snow does 78221 get?

About 29.7 inches of precipitation a year (NOAA 1991–2020 normals, San Antonio Stinson Airport station).

How hot do summers get in San Antonio, TX?

The average high peaks at 98 °F in August, with about 134 days a year at 90 °F or more.

What kind of soil does 78221 have?

The USDA soil survey maps Loire at the center of ZIP 78221: clay loam, well drained, pH about 8.2 (alkaline).

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

Spring leaf-out near 78221 came on Jan 15 in 2026, 9 days earlier than the 1991–2020 average (Jan 24), 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 78221 is 14 h 01 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.