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

Planting zone for 78115 — Geronimo, TX

ZIP code 78115 (Geronimo, Guadalupe County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is March 8 and the first fall frost November 18.

Where ZIP 78115 is

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 frostMar 8
First frostNov 18
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 Geronimo, 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 Geronimo, TX

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 8median — 50% chance of a later frost
Safe for tender plantsApril 1only 10% chance of frost after
First fall frostNovember 18median — 10% chance by Nov 2
Growing season253 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 24 and returns around December 2.

From the NOAA station New Braunfels, TX — 11 miles away, elevation 722 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 78115

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 25 – Feb 8
SpinachSow outdoors · Jan 25 – Feb 15
Broccoli, cabbageStart indoors · Dec 28 – Jan 11
Broccoli, cabbageTransplant · Feb 15 – Mar 1
Onion setsPlant outdoors · Feb 8 – Feb 22
PotatoesPlant outdoors · Feb 15 – Mar 1
LettuceSow outdoors · Feb 8 – Feb 22
Carrots, beetsSow outdoors · Feb 15 – Mar 1
TomatoesStart indoors · Jan 11 – Jan 25
TomatoesTransplant · Mar 15 – Mar 29
Peppers, eggplantStart indoors · Dec 28 – Jan 11
Peppers, eggplantTransplant · Mar 22 – Apr 5
BeansSow outdoors · Mar 15 – Mar 29
Sweet cornSow outdoors · Mar 15 – Mar 29
Cucumbers, squashSow outdoors · Mar 15 – Mar 29
Fall lettuce, spinachSow outdoors · Sep 23 – Oct 7
GarlicPlant cloves · Nov 4 – Dec 9
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 8) and first fall frost (Nov 18) 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 78115 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).

Soil in Geronimo, TX

The soil mapped at the center of ZIP 78115 is Heiden — clay, well drained.

TextureClayholds water and nutrients; slow to drain and warm up
pH8.2alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Heiden clay, 3 to 5 percent slopes, eroded.

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 78115; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Geronimo, TX

Summer high95 °Faverage high, August
Winter low37 °Faverage low, January
Hot days117days a year at 90 °F or more
Freezing nights32nights a year at 32 °F or less
Growing degree days6,606base 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
Precipitation35.8 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 62 °F, low 37 °F 62°37° JanFebruary: average high 66 °F, low 40 °F 66°40° FebMarch: average high 73 °F, low 48 °F 73°48° MarApril: average high 79 °F, low 54 °F 79°54° AprMay: average high 85 °F, low 64 °F 85°64° MayJune: average high 90 °F, low 70 °F 90°70° JunJuly: average high 93 °F, low 72 °F 93°72° JulAugust: average high 95 °F, low 71 °F 95°71° AugSeptember: average high 89 °F, low 66 °F 89°66° SepOctober: average high 81 °F, low 56 °F 81°56° OctNovember: average high 71 °F, low 46 °F 71°46° NovDecember: average high 63 °F, low 40 °F 63°40° Dec

Precipitation by month inches

0″1″2″3″4″January: 2.34 in precipitation 2.3 JanFebruary: 1.80 in precipitation 1.8 FebMarch: 2.73 in precipitation 2.7 MarApril: 2.60 in precipitation 2.6 AprMay: 3.89 in precipitation 3.9 MayJune: 3.80 in precipitation 3.8 JunJuly: 2.59 in precipitation 2.6 JulAugust: 2.39 in precipitation 2.4 AugSeptember: 3.96 in precipitation 4.0 SepOctober: 3.87 in precipitation 3.9 OctNovember: 3.09 in precipitation 3.1 NovDecember: 2.73 in precipitation 2.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: New Braunfels, TX (11 mi away); precipitation: Mcqueeney 0.5 Ene, TX (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9a.

781239a
Mc Queeney, TX · 4 mi
781569a
Seguin, TX · 6 mi
781559a
Seguin, TX · 6 mi
781249a
Marion, TX · 6 mi
781309a
New Braunfels, TX · 10 mi
781089a
Cibolo, TX · 11 mi
781319a
New Braunfels, TX · 12 mi
781359a
New Braunfels, TX · 12 mi

Texas planting zones →

Questions about 78115

What planting zone is ZIP code 78115?

ZIP code 78115 (Geronimo, 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 Geronimo, TX?

The median last spring frost (32 °F) near 78115 is March 8; after April 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, New Braunfels station.

When is the first frost in Geronimo, TX?

The median first fall frost near 78115 is November 18, giving a median frost-free growing season of 253 days.

When should I plant tomatoes in 78115?

Start tomato seeds indoors around Jan 11 – Jan 25 and set transplants outside around Mar 15 – Mar 29, one to three weeks after the median last frost.

How much rain and snow does 78115 get?

About 35.8 inches of precipitation a year (NOAA 1991–2020 normals, Mcqueeney 0.5 Ene station).

How hot do summers get in Geronimo, TX?

The average high peaks at 95 °F in August, with about 117 days a year at 90 °F or more.

What kind of soil does 78115 have?

The USDA soil survey maps Heiden at the center of ZIP 78115: clay, well drained, pH about 8.2 (alkaline).

Did spring come early in Geronimo, TX in 2026?

Spring leaf-out near 78115 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 Geronimo, TX?

Short-day onions: the longest day near 78115 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 78115 change?

Yes. The 2012 USDA map put 78115 in zone 8b; the 2023 map puts it in zone 9a. The newer map uses 1991–2020 data and more weather stations.