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

Planting zone for Merrillville, IN

Merrillville, IN is in USDA zone 6a across its 2 ZIP codes. The median last spring frost is April 22 and the first fall frost October 25.

Merrillville on the zone map

Outlined: its 1 ZIP code areas · 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
ZIP codes2
Last frostApr 22
First frostOct 25
Growing season185 days

6a 2 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Merrillville, 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 Merrillville, IN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 22median — 50% chance of a later frost
Safe for tender plantsMay 6only 10% chance of frost after
First fall frostOctober 25median — 10% chance by Oct 12
Growing season185 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 9 and returns around November 5.

From the NOAA station Valparaiso Wtr Wks, IN, elevation 801 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 Merrillville

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 11 – Mar 25
SpinachSow outdoors · Mar 11 – Apr 1
Broccoli, cabbageStart indoors · Feb 11 – Feb 25
Broccoli, cabbageTransplant · Apr 1 – Apr 15
Onion setsPlant outdoors · Mar 25 – Apr 8
PotatoesPlant outdoors · Apr 1 – Apr 15
LettuceSow outdoors · Mar 25 – Apr 8
Carrots, beetsSow outdoors · Apr 1 – Apr 15
TomatoesStart indoors · Feb 25 – Mar 11
TomatoesTransplant · Apr 29 – May 13
Peppers, eggplantStart indoors · Feb 11 – Feb 25
Peppers, eggplantTransplant · May 6 – May 20
BeansSow outdoors · Apr 29 – May 13
Sweet cornSow outdoors · Apr 29 – May 13
Cucumbers, squashSow outdoors · Apr 29 – May 13
Fall lettuce, spinachSow outdoors · Aug 30 – Sep 13
GarlicPlant cloves · Oct 11 – Nov 15
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 22) and first fall frost (Oct 25) 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 46410 came on Mar 21 — 14 days earlier than the 1991–2020 average (Apr 4).

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 Merrillville, IN.

Soil in Merrillville, IN

The soil mapped at the center of ZIP 46410 is Milford — silt loam, very poorly drained.

TextureSilt loama good balance for most vegetables
pH6.5neutral; most vegetables like 6.0–7.0
DrainageVery poorly drainedconsider raised beds
Organic matter2%moderate
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Milford silt loam, 0 to 2 percent slopes, overwash.

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 46410; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Merrillville, IN

Summer high83 °Faverage high, July
Winter low18 °Faverage low, January
Hot days9days a year at 90 °F or more
Freezing nights124nights a year at 32 °F or less
Growing degree days3,084base 50 °F — the season’s usable heat
Longest day15 h 11 mindaylight on June 21
Shortest day9 h 10 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation40.9 inper year, rain and melted snow
Snowfall27 inper year; 29 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 18 °F 32°18° JanFebruary: average high 36 °F, low 21 °F 36°21° FebMarch: average high 48 °F, low 29 °F 48°29° MarApril: average high 61 °F, low 39 °F 61°39° AprMay: average high 71 °F, low 49 °F 71°49° MayJune: average high 80 °F, low 59 °F 80°59° JunJuly: average high 83 °F, low 63 °F 83°63° JulAugust: average high 81 °F, low 62 °F 81°62° AugSeptember: average high 75 °F, low 54 °F 75°54° SepOctober: average high 64 °F, low 44 °F 64°44° OctNovember: average high 49 °F, low 34 °F 49°34° NovDecember: average high 37 °F, low 24 °F 37°24° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 2.49 in precipitation, 10.3 in snowfall 2.5❄10 JanFebruary: 2.00 in precipitation, 6.3 in snowfall 2.0❄6 FebMarch: 2.29 in precipitation, 4.3 in snowfall 2.3❄4 MarApril: 3.70 in precipitation, 0.6 in snowfall 3.7❄1 AprMay: 4.33 in precipitation 4.3 MayJune: 4.68 in precipitation 4.7 JunJuly: 4.17 in precipitation 4.2 JulAugust: 5.22 in precipitation 5.2 AugSeptember: 3.48 in precipitation 3.5 SepOctober: 3.54 in precipitation 3.5 OctNovember: 2.75 in precipitation, 0.4 in snowfall 2.8 NovDecember: 2.23 in precipitation, 4.7 in snowfall 2.2❄5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Valparaiso Wtr Wks, IN (16 mi away); precipitation: Crown Pt 1n, IN (3 mi away). Daylight is calculated from latitude.

ZIP codes in Merrillville

464106a
−10 to −5 °F
464116a
−10 to −5 °F

Indiana planting zones →

Questions about Merrillville

What planting zone is Merrillville, IN?

Merrillville, IN is in USDA hardiness zone 6a on the 2023 map (6a: −10 to −5 °F).

When is the last frost in Merrillville, IN?

The median last spring frost is April 22 and the median first fall frost is October 25 (NOAA 1991–2020 normals, Valparaiso Wtr Wks station).

When can I plant a garden in Merrillville, IN?

Cool-season crops like peas and spinach go in around Mar 11 – Apr 1; tomatoes, peppers, beans and squash after about Apr 29, once frost risk has passed.

What kind of onions grow in Merrillville, IN?

Long-day onions: the longest day is 15 h 11 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

How much rain and snow does Merrillville, IN get?

About 40.9 inches of precipitation a year and 27 inches of snowfall (NOAA 1991–2020 normals).