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

Planting zone for 78384 — San Diego, TX

ZIP code 78384 (San Diego, Duval County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is February 20 and the first fall frost December 1.

Where ZIP 78384 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.

Zone9b25 to 30 °F

Coldest night−3.9 to −1.1 °C

Last frostFeb 20

First frostDec 1

2012 zone9a

Was 9a 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 9b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for San Diego, 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 Diego, 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 14only 10% chance of frost after

First fall frostDecember 1median — 10% chance by Nov 10

Growing season286 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 29 and returns around December 18.

From the NOAA station Benavides 2, TX — 10 miles away, elevation 381 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 78384

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 6 – Oct 20

GarlicPlant cloves · Nov 17 – Dec 22

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 20) and first fall frost (Dec 1) 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 78384 came on Jan 10 — 10 days earlier than the 1991–2020 average (Jan 20).

average
Jan 202026
Jan 10

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).

Soil in San Diego, TX

The soil mapped at the center of ZIP 78384 is Piedras — gravelly fine sandy loam, well drained.

TextureGravelly fine sandy loamdrains and warms fast; dries out and needs more feeding

pH7.2neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Piedras and Cuevitas soils, 1 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 78384; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in San Diego, TX

Summer high98 °Faverage high, August

Winter low43 °Faverage low, January

Hot days152days a year at 90 °F or more

Freezing nights15nights a year at 32 °F or less

Growing degree days8,218base 50 °F — the season’s usable heat

Longest day13 h 54 mindaylight on June 21

Shortest day10 h 23 mindaylight on December 21

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

Precipitation25.1 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: Benavides 2, TX (10 mi away); precipitation: Freer, TX (13 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9b.

783419b

Benavides, TX · 11 mi

Concepcion, TX · 27 mi

Texas planting zones →

Questions about 78384

What planting zone is ZIP code 78384?

ZIP code 78384 (San Diego, TX) is in USDA hardiness zone 9b on the 2023 map: the coldest night of an average winter reaches 25 to 30 °F (−3.9 to −1.1 °C).

When is the last frost in San Diego, TX?

The median last spring frost (32 °F) near 78384 is February 20; after March 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Benavides 2 station.

When is the first frost in San Diego, TX?

The median first fall frost near 78384 is December 1, giving a median frost-free growing season of 286 days.

When should I plant tomatoes in 78384?

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 78384 get?

About 25.1 inches of precipitation a year (NOAA 1991–2020 normals, Freer station).

How hot do summers get in San Diego, TX?

The average high peaks at 98 °F in August, with about 152 days a year at 90 °F or more.

What kind of soil does 78384 have?

The USDA soil survey maps Piedras at the center of ZIP 78384: gravelly fine sandy loam, well drained, pH about 7.2 (neutral).

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

Spring leaf-out near 78384 came on Jan 10 in 2026, 10 days earlier than the 1991–2020 average (Jan 20), according to the USA National Phenology Network Spring Index.

What kind of onions grow in San Diego, TX?

Short-day onions: the longest day near 78384 is 13 h 54 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.

Did the zone for 78384 change?

Yes. The 2012 USDA map put 78384 in zone 9a; the 2023 map puts it in zone 9b. The newer map uses 1991–2020 data and more weather stations.