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

Planting zone for 46071 — Thorntown, IN

ZIP code 46071 (Thorntown, Boone County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 27 and the first fall frost October 12.

Where ZIP 46071 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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostApr 27
First frostOct 12
2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Thorntown, IN…

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 Thorntown, IN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 27median — 50% chance of a later frost
Safe for tender plantsMay 13only 10% chance of frost after
First fall frostOctober 12median — 10% chance by Sep 26
Growing season167 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 14 and returns around October 23.

From the NOAA station Crawfordsville 6 Se, IN — 12 miles away, elevation 837 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 46071

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 16 – Mar 30
SpinachSow outdoors · Mar 16 – Apr 6
Broccoli, cabbageStart indoors · Feb 16 – Mar 2
Broccoli, cabbageTransplant · Apr 6 – Apr 20
Onion setsPlant outdoors · Mar 30 – Apr 13
PotatoesPlant outdoors · Apr 6 – Apr 20
LettuceSow outdoors · Mar 30 – Apr 13
Carrots, beetsSow outdoors · Apr 6 – Apr 20
TomatoesStart indoors · Mar 2 – Mar 16
TomatoesTransplant · May 4 – May 18
Peppers, eggplantStart indoors · Feb 16 – Mar 2
Peppers, eggplantTransplant · May 11 – May 25
BeansSow outdoors · May 4 – May 18
Sweet cornSow outdoors · May 4 – May 18
Cucumbers, squashSow outdoors · May 4 – May 18
Fall lettuce, spinachSow outdoors · Aug 17 – Aug 31
GarlicPlant cloves · Sep 28 – Nov 2
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 27) and first fall frost (Oct 12) 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 46071 came on Mar 10 — 18 days earlier than the 1991–2020 average (Mar 28).

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 6a in Indiana

558 plants native to the lower 48 states, recorded in Indiana, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

Trees 71

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 105

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °F

Wildflowers & perennials 200

American bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °FAmerican speedwell0.8 ft · blooms mid summer · low shade tolerance · to −38 °F

Grasses 161

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °FBicknell's sedge3 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 9

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fcatbird grape30 ft · blooms late spring · medium shade tolerance · to −13 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low 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 Thorntown, IN.

Soil in Thorntown, IN

The soil mapped at the center of ZIP 46071 is Treaty — silty clay loam, poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up
pH6.5neutral; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter4.5%moderate
Hydrologic groupB/Dmoderate when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Treaty silty clay loam, 0 to 1 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 46071; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Thorntown, IN

Summer high83 °Faverage high, July
Winter low17 °Faverage low, January
Hot days12days a year at 90 °F or more
Freezing nights140nights a year at 32 °F or less
Growing degree days3,079base 50 °F — the season’s usable heat
Longest day15 h 02 mindaylight on June 21
Shortest day9 h 19 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation41.3 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 33 °F, low 17 °F 33°17° JanFebruary: average high 38 °F, low 20 °F 38°20° FebMarch: average high 49 °F, low 29 °F 49°29° MarApril: average high 61 °F, low 39 °F 61°39° AprMay: average high 72 °F, low 50 °F 72°50° MayJune: average high 80 °F, low 60 °F 80°60° JunJuly: average high 83 °F, low 62 °F 83°62° JulAugust: average high 82 °F, low 59 °F 82°59° AugSeptember: average high 77 °F, low 52 °F 77°52° SepOctober: average high 65 °F, low 41 °F 65°41° OctNovember: average high 50 °F, low 31 °F 50°31° NovDecember: average high 38 °F, low 23 °F 38°23° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 2.87 in precipitation 2.9 JanFebruary: 2.24 in precipitation 2.2 FebMarch: 2.97 in precipitation 3.0 MarApril: 4.23 in precipitation 4.2 AprMay: 4.30 in precipitation 4.3 MayJune: 4.88 in precipitation 4.9 JunJuly: 4.35 in precipitation 4.3 JulAugust: 3.44 in precipitation 3.4 AugSeptember: 2.94 in precipitation 2.9 SepOctober: 3.22 in precipitation 3.2 OctNovember: 3.30 in precipitation 3.3 NovDecember: 2.55 in precipitation 2.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Crawfordsville 6 Se, IN (12 mi away); precipitation: Thorntown 3.4 Sw, IN (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

460356a
Colfax, IN · 7 mi
479406a
Darlington, IN · 7 mi
461026a
Advance, IN · 8 mi
460526a
Lebanon, IN · 9 mi
461476a
Jamestown, IN · 10 mi
479306a
Clarks Hill, IN · 11 mi
479686a
New Ross, IN · 13 mi
460416a
Frankfort, IN · 14 mi

Indiana planting zones →

Questions about 46071

What planting zone is ZIP code 46071?

ZIP code 46071 (Thorntown, IN) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Thorntown, IN?

The median last spring frost (32 °F) near 46071 is April 27; after May 13 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Crawfordsville 6 Se station.

When is the first frost in Thorntown, IN?

The median first fall frost near 46071 is October 12, giving a median frost-free growing season of 167 days.

When should I plant tomatoes in 46071?

Start tomato seeds indoors around Mar 2 – Mar 16 and set transplants outside around May 4 – May 18, one to three weeks after the median last frost.

How much rain and snow does 46071 get?

About 41.3 inches of precipitation a year (NOAA 1991–2020 normals, Thorntown 3.4 Sw station).

How hot do summers get in Thorntown, IN?

The average high peaks at 83 °F in July, with about 12 days a year at 90 °F or more.

What kind of soil does 46071 have?

The USDA soil survey maps Treaty at the center of ZIP 46071: silty clay loam, poorly drained, pH about 6.5 (neutral).

Did spring come early in Thorntown, IN in 2026?

Spring leaf-out near 46071 came on Mar 10 in 2026, 18 days earlier than the 1991–2020 average (Mar 28), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Thorntown, IN?

Long-day onions: the longest day near 46071 is 15 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 46071 change?

Yes. The 2012 USDA map put 46071 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.