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

Planting zone for 46971 — Grissom Arb, IN

ZIP code 46971 (Grissom Arb, Miami County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 25 and the first fall frost October 17.

Where ZIP 46971 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 25
First frostOct 17
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 Grissom Arb, 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 Grissom Arb, IN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 25median — 50% chance of a later frost
Safe for tender plantsMay 11only 10% chance of frost after
First fall frostOctober 17median — 10% chance by Oct 1
Growing season174 daysfrost-free, median

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

From the NOAA station Young America, IN — 12 miles away, elevation 774 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 46971

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 14 – Mar 28
SpinachSow outdoors · Mar 14 – Apr 4
Broccoli, cabbageStart indoors · Feb 14 – Feb 28
Broccoli, cabbageTransplant · Apr 4 – Apr 18
Onion setsPlant outdoors · Mar 28 – Apr 11
PotatoesPlant outdoors · Apr 4 – Apr 18
LettuceSow outdoors · Mar 28 – Apr 11
Carrots, beetsSow outdoors · Apr 4 – Apr 18
TomatoesStart indoors · Feb 28 – Mar 14
TomatoesTransplant · May 2 – May 16
Peppers, eggplantStart indoors · Feb 14 – Feb 28
Peppers, eggplantTransplant · May 9 – May 23
BeansSow outdoors · May 2 – May 16
Sweet cornSow outdoors · May 2 – May 16
Cucumbers, squashSow outdoors · May 2 – May 16
Fall lettuce, spinachSow outdoors · Aug 22 – Sep 5
GarlicPlant cloves · Oct 3 – Nov 7
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 25) and first fall frost (Oct 17) 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 46971 came on Mar 12 — 20 days earlier than the 1991–2020 average (Apr 1).

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 Grissom Arb, IN.

Soil in Grissom Arb, IN

The soil mapped at the center of ZIP 46971 is Treaty — silt loam, poorly drained.

TextureSilt loama good balance for most vegetables
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 silt loam, 0 to 2 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 46971; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Grissom Arb, IN

Summer high83 °Faverage high, July
Winter low17 °Faverage low, January
Hot days12days a year at 90 °F or more
Freezing nights130nights a year at 32 °F or less
Growing degree days3,063base 50 °F — the season’s usable heat
Longest day15 h 05 mindaylight on June 21
Shortest day9 h 15 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation41.1 inper year, rain and melted snow
Snowfall21 inper year; 28 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 32 °F, low 17 °F 32°17° JanFebruary: average high 36 °F, low 20 °F 36°20° FebMarch: average high 47 °F, low 29 °F 47°29° MarApril: average high 60 °F, low 38 °F 60°38° 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 81 °F, low 60 °F 81°60° AugSeptember: average high 77 °F, low 52 °F 77°52° SepOctober: average high 64 °F, low 42 °F 64°42° OctNovember: average high 49 °F, low 32 °F 49°32° NovDecember: average high 37 °F, low 23 °F 37°23° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 2.55 in precipitation, 7.8 in snowfall 2.5❄8 JanFebruary: 2.25 in precipitation, 5 in snowfall 2.3❄5 FebMarch: 2.92 in precipitation, 2.9 in snowfall 2.9❄3 MarApril: 3.92 in precipitation, 0.3 in snowfall 3.9 AprMay: 4.37 in precipitation 4.4 MayJune: 4.99 in precipitation 5.0 JunJuly: 4.24 in precipitation 4.2 JulAugust: 4.15 in precipitation 4.2 AugSeptember: 3.32 in precipitation 3.3 SepOctober: 2.83 in precipitation 2.8 OctNovember: 3.26 in precipitation, 0.6 in snowfall 3.3❄1 NovDecember: 2.28 in precipitation, 4.3 in snowfall 2.3❄4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Young America, IN (12 mi away); precipitation: Peru, IN (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

469146a
Bunker Hill, IN · 4 mi
469596a
Miami, IN · 4 mi
469946a
Walton, IN · 5 mi
469326a
Galveston, IN · 7 mi
469616a
New Waverly, IN · 8 mi
469706a
Peru, IN · 9 mi
469016a
Kokomo, IN · 9 mi
469586a
Mexico, IN · 11 mi

Indiana planting zones →

Questions about 46971

What planting zone is ZIP code 46971?

ZIP code 46971 (Grissom Arb, 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 Grissom Arb, IN?

The median last spring frost (32 °F) near 46971 is April 25; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Young America station.

When is the first frost in Grissom Arb, IN?

The median first fall frost near 46971 is October 17, giving a median frost-free growing season of 174 days.

When should I plant tomatoes in 46971?

Start tomato seeds indoors around Feb 28 – Mar 14 and set transplants outside around May 2 – May 16, one to three weeks after the median last frost.

How much rain and snow does 46971 get?

About 41.1 inches of precipitation a year and 21 inches of snowfall (NOAA 1991–2020 normals, Peru station).

How hot do summers get in Grissom Arb, 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 46971 have?

The USDA soil survey maps Treaty at the center of ZIP 46971: silt loam, poorly drained, pH about 6.5 (neutral).

Did spring come early in Grissom Arb, IN in 2026?

Spring leaf-out near 46971 came on Mar 12 in 2026, 20 days earlier than the 1991–2020 average (Apr 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Grissom Arb, IN?

Long-day onions: the longest day near 46971 is 15 h 05 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 46971 change?

Yes. The 2012 USDA map put 46971 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.