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

Planting zone for 46231 — Indianapolis, IN

ZIP code 46231 (Indianapolis, Marion County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 12 and the first fall frost October 27.

Where ZIP 46231 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.

Zone6b−5 to 0 °F
Coldest night−20.6 to −17.8 °C
Last frostApr 12
First frostOct 27
2012 zone6a

Was 6a 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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Indianapolis, 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 Indianapolis, IN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 12median — 50% chance of a later frost
Safe for tender plantsApril 28only 10% chance of frost after
First fall frostOctober 27median — 10% chance by Oct 14
Growing season196 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 1 and returns around November 5.

From the NOAA station Indianapolis Nwfo, IN — 3 miles away, elevation 791 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 46231

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 1 – Mar 15
SpinachSow outdoors · Mar 1 – Mar 22
Broccoli, cabbageStart indoors · Feb 1 – Feb 15
Broccoli, cabbageTransplant · Mar 22 – Apr 5
Onion setsPlant outdoors · Mar 15 – Mar 29
PotatoesPlant outdoors · Mar 22 – Apr 5
LettuceSow outdoors · Mar 15 – Mar 29
Carrots, beetsSow outdoors · Mar 22 – Apr 5
TomatoesStart indoors · Feb 15 – Mar 1
TomatoesTransplant · Apr 19 – May 3
Peppers, eggplantStart indoors · Feb 1 – Feb 15
Peppers, eggplantTransplant · Apr 26 – May 10
BeansSow outdoors · Apr 19 – May 3
Sweet cornSow outdoors · Apr 19 – May 3
Cucumbers, squashSow outdoors · Apr 19 – May 3
Fall lettuce, spinachSow outdoors · Sep 1 – Sep 15
GarlicPlant cloves · Oct 13 – Nov 17
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 12) and first fall frost (Oct 27) 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 46231 came on Mar 8 — 17 days earlier than the 1991–2020 average (Mar 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).

Native plants for zone 6b in Indiana

564 plants native to the lower 48 states, recorded in Indiana, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Trees 72

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 202

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 162

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °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 °F

Vines 11

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 °Fgraybark grape50 ft · blooms late spring · medium shade tolerance · to −8 °Fheartleaf peppervine2 ft · blooms late spring · low shade tolerance · to −8 °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 Indianapolis, IN.

Soil in Indianapolis, IN

The soil mapped at the center of ZIP 46231 is Crosby — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables
pH7.2neutral; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter2.5%moderate
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Crosby silt loam, fine-loamy subsoil, 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 46231; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Indianapolis, IN

Summer high85 °Faverage high, July
Winter low19 °Faverage low, January
Hot days25days a year at 90 °F or more
Freezing nights108nights a year at 32 °F or less
Growing degree days3,717base 50 °F — the season’s usable heat
Longest day14 h 59 mindaylight on June 21
Shortest day9 h 21 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation45.3 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 36 °F, low 19 °F 36°19° JanFebruary: average high 40 °F, low 23 °F 40°23° FebMarch: average high 51 °F, low 32 °F 51°32° MarApril: average high 64 °F, low 43 °F 64°43° AprMay: average high 74 °F, low 54 °F 74°54° MayJune: average high 82 °F, low 63 °F 82°63° JunJuly: average high 85 °F, low 67 °F 85°67° JulAugust: average high 84 °F, low 65 °F 84°65° AugSeptember: average high 78 °F, low 57 °F 78°57° SepOctober: average high 66 °F, low 45 °F 66°45° OctNovember: average high 52 °F, low 34 °F 52°34° NovDecember: average high 40 °F, low 25 °F 40°25° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.15 in precipitation 3.1 JanFebruary: 2.46 in precipitation 2.5 FebMarch: 3.67 in precipitation 3.7 MarApril: 4.50 in precipitation 4.5 AprMay: 5.00 in precipitation 5.0 MayJune: 5.39 in precipitation 5.4 JunJuly: 4.56 in precipitation 4.6 JulAugust: 3.42 in precipitation 3.4 AugSeptember: 3.36 in precipitation 3.4 SepOctober: 3.29 in precipitation 3.3 OctNovember: 3.57 in precipitation 3.6 NovDecember: 2.92 in precipitation 2.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Indianapolis Nwfo, IN (3 mi away); precipitation: Speedway 6.2 Ssw, IN (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

462416b
Indianapolis, IN · 3 mi
461686a
Plainfield, IN · 4 mi
461236a
Avon, IN · 5 mi
462146b
Indianapolis, IN · 5 mi
462216b
Indianapolis, IN · 5 mi
462346a
Indianapolis, IN · 6 mi
461136a
Camby, IN · 6 mi
462246b
Indianapolis, IN · 6 mi

All 56 ZIP codes in Indianapolis → · Indiana planting zones →

Questions about 46231

What planting zone is ZIP code 46231?

ZIP code 46231 (Indianapolis, IN) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Indianapolis, IN?

The median last spring frost (32 °F) near 46231 is April 12; after April 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Indianapolis Nwfo station.

When is the first frost in Indianapolis, IN?

The median first fall frost near 46231 is October 27, giving a median frost-free growing season of 196 days.

When should I plant tomatoes in 46231?

Start tomato seeds indoors around Feb 15 – Mar 1 and set transplants outside around Apr 19 – May 3, one to three weeks after the median last frost.

How much rain and snow does 46231 get?

About 45.3 inches of precipitation a year (NOAA 1991–2020 normals, Speedway 6.2 Ssw station).

How hot do summers get in Indianapolis, IN?

The average high peaks at 85 °F in July, with about 25 days a year at 90 °F or more.

What kind of soil does 46231 have?

The USDA soil survey maps Crosby at the center of ZIP 46231: silt loam, somewhat poorly drained, pH about 7.2 (neutral).

Did spring come early in Indianapolis, IN in 2026?

Spring leaf-out near 46231 came on Mar 8 in 2026, 17 days earlier than the 1991–2020 average (Mar 25), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Indianapolis, IN?

Intermediate onions: the longest day near 46231 is 14 h 59 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 46231 change?

Yes. The 2012 USDA map put 46231 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.