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

Planting zone for 78631 — Harper, TX

ZIP code 78631 (Harper, Gillespie County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is March 15 and the first fall frost November 15.

Where ZIP 78631 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.

Zone8a10 to 15 °F

Coldest night−12.2 to −9.4 °C

Last frostMar 15

First frostNov 15

2012 zone8a

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 8a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Harper, 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 Harper, TX

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMarch 15median — 50% chance of a later frost

Safe for tender plantsApril 12only 10% chance of frost after

First fall frostNovember 15median — 10% chance by Oct 27

Growing season243 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 2 and returns around November 29.

From the NOAA station Harper 3ene, TX — 7 miles away, elevation 2,110 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 78631

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 1 – Feb 15

SpinachSow outdoors · Feb 1 – Feb 22

Broccoli, cabbageStart indoors · Jan 4 – Jan 18

Broccoli, cabbageTransplant · Feb 22 – Mar 8

Onion setsPlant outdoors · Feb 15 – Mar 1

PotatoesPlant outdoors · Feb 22 – Mar 8

LettuceSow outdoors · Feb 15 – Mar 1

Carrots, beetsSow outdoors · Feb 22 – Mar 8

TomatoesStart indoors · Jan 18 – Feb 1

TomatoesTransplant · Mar 22 – Apr 5

Peppers, eggplantStart indoors · Jan 4 – Jan 18

Peppers, eggplantTransplant · Mar 29 – Apr 12

BeansSow outdoors · Mar 22 – Apr 5

Sweet cornSow outdoors · Mar 22 – Apr 5

Cucumbers, squashSow outdoors · Mar 22 – Apr 5

Fall lettuce, spinachSow outdoors · Sep 20 – Oct 4

GarlicPlant cloves · Nov 1 – Dec 6

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 15) and first fall frost (Nov 15) 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 78631 came on Feb 6 — 3 days later than the 1991–2020 average (Feb 3).

average
Feb 32026
Feb 6

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 8a in Texas

601 plants native to the lower 48 states, recorded in Texas, and rated by the USDA to survive 10 °F or colder — the bottom of zone 8a. 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 Harper, TX.

Soil in Harper, TX

The soil mapped at the center of ZIP 78631 is Eckrant — cobbly clay, well drained.

TextureCobbly 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 matter6.5%high

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Eckrant-Tarrant complex, undulating.

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 78631; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Harper, TX

Summer high93 °Faverage high, August

Winter low34 °Faverage low, January

Hot days86days a year at 90 °F or more

Freezing nights41nights a year at 32 °F or less

Growing degree days5,899base 50 °F — the season’s usable heat

Longest day14 h 06 mindaylight on June 21

Shortest day10 h 11 mindaylight on December 21

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

Precipitation29.5 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: Harper 3ene, TX (7 mi away); precipitation: Harper 1.0 Nw, TX (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Kerrville, TX · 23 mi

780588a

Mountain Home, TX · 24 mi

Fredericksburg, TX · 26 mi

Texas planting zones →

Questions about 78631

What planting zone is ZIP code 78631?

ZIP code 78631 (Harper, TX) is in USDA hardiness zone 8a on the 2023 map: the coldest night of an average winter reaches 10 to 15 °F (−12.2 to −9.4 °C).

When is the last frost in Harper, TX?

The median last spring frost (32 °F) near 78631 is March 15; after April 12 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Harper 3ene station.

When is the first frost in Harper, TX?

The median first fall frost near 78631 is November 15, giving a median frost-free growing season of 243 days.

When should I plant tomatoes in 78631?

Start tomato seeds indoors around Jan 18 – Feb 1 and set transplants outside around Mar 22 – Apr 5, one to three weeks after the median last frost.

How much rain and snow does 78631 get?

About 29.5 inches of precipitation a year (NOAA 1991–2020 normals, Harper 1.0 Nw station).

How hot do summers get in Harper, TX?

The average high peaks at 93 °F in August, with about 86 days a year at 90 °F or more.

What kind of soil does 78631 have?

The USDA soil survey maps Eckrant at the center of ZIP 78631: cobbly clay, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in Harper, TX in 2026?

Spring leaf-out near 78631 came on Feb 6 in 2026, 3 days later than the 1991–2020 average (Feb 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Harper, TX?

Short-day onions: the longest day near 78631 is 14 h 06 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.