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

Planting zone for 65321 — Blackburn, MO

ZIP code 65321 (Blackburn, Saline County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 17 and the first fall frost October 20.

Where ZIP 65321 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 17
First frostOct 20
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 Blackburn, MO…

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 Blackburn, MO

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 17median — 50% chance of a later frost
Safe for tender plantsMay 2only 10% chance of frost after
First fall frostOctober 20median — 10% chance by Oct 1
Growing season184 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 4 and returns around October 29.

From the NOAA station Sweet Springs, MO — 7 miles away, elevation 676 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 65321

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 6 – Mar 20
SpinachSow outdoors · Mar 6 – Mar 27
Broccoli, cabbageStart indoors · Feb 6 – Feb 20
Broccoli, cabbageTransplant · Mar 27 – Apr 10
Onion setsPlant outdoors · Mar 20 – Apr 3
PotatoesPlant outdoors · Mar 27 – Apr 10
LettuceSow outdoors · Mar 20 – Apr 3
Carrots, beetsSow outdoors · Mar 27 – Apr 10
TomatoesStart indoors · Feb 20 – Mar 6
TomatoesTransplant · Apr 24 – May 8
Peppers, eggplantStart indoors · Feb 6 – Feb 20
Peppers, eggplantTransplant · May 1 – May 15
BeansSow outdoors · Apr 24 – May 8
Sweet cornSow outdoors · Apr 24 – May 8
Cucumbers, squashSow outdoors · Apr 24 – May 8
Fall lettuce, spinachSow outdoors · Aug 25 – Sep 8
GarlicPlant cloves · Oct 6 – Nov 10
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 17) and first fall frost (Oct 20) 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 65321 came on Mar 3 — 15 days earlier than the 1991–2020 average (Mar 18).

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 Missouri

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

Trees 70

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 °Fbald cypress130 ft · blooms mid spring · medium shade tolerance · to −18 °F

Shrubs 83

alternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican beautyberry6 ft · blooms early summer · medium shade tolerance · to −8 °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 °FAmerican hornbeam30 ft · blooms mid spring · low shade tolerance · to −34 °F

Wildflowers & perennials 192

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °FAmerican 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 °F

Grasses 157

alkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBicknell's sedge3 ft · blooms late spring · low shade tolerance · to −38 °Fbig bluestem6 ft · blooms summer · high shade tolerance · to −46 °Fblister sedge3 ft · blooms late spring · medium shade tolerance · to −38 °F

Vines 12

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 Blackburn, MO.

Soil in Blackburn, MO

The soil mapped at the center of ZIP 65321 is Greenton — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables
pH6.4slightly acidic; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter3.6%moderate
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Greenton silt loam, 5 to 9 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 65321; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Blackburn, MO

Summer high89 °Faverage high, July
Winter low17 °Faverage low, January
Hot days37days a year at 90 °F or more
Freezing nights112nights a year at 32 °F or less
Growing degree days3,921base 50 °F — the season’s usable heat
Longest day14 h 55 mindaylight on June 21
Shortest day9 h 25 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation42.6 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 38 °F, low 17 °F 38°17° JanFebruary: average high 44 °F, low 22 °F 44°22° FebMarch: average high 56 °F, low 32 °F 56°32° MarApril: average high 66 °F, low 42 °F 66°42° AprMay: average high 76 °F, low 53 °F 76°53° MayJune: average high 84 °F, low 63 °F 84°63° JunJuly: average high 89 °F, low 67 °F 89°67° JulAugust: average high 87 °F, low 65 °F 87°65° AugSeptember: average high 80 °F, low 56 °F 80°56° SepOctober: average high 69 °F, low 43 °F 69°43° OctNovember: average high 55 °F, low 32 °F 55°32° NovDecember: average high 43 °F, low 23 °F 43°23° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 1.60 in precipitation 1.6 JanFebruary: 1.85 in precipitation 1.9 FebMarch: 2.92 in precipitation 2.9 MarApril: 4.10 in precipitation 4.1 AprMay: 5.56 in precipitation 5.6 MayJune: 5.69 in precipitation 5.7 JunJuly: 4.66 in precipitation 4.7 JulAugust: 3.97 in precipitation 4.0 AugSeptember: 4.02 in precipitation 4.0 SepOctober: 3.73 in precipitation 3.7 OctNovember: 2.55 in precipitation 2.5 NovDecember: 1.96 in precipitation 2.0 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Sweet Springs, MO (7 mi away); precipitation: Blackburn 3.0 Nne, MO (5 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

640016b
Alma, MO · 5 mi
653516b
Sweet Springs, MO · 7 mi
653276b
Emma, MO · 7 mi
653396b
Malta Bend, MO · 9 mi
640216b
Corder, MO · 10 mi
640966b
Waverly, MO · 10 mi
640206b
Concordia, MO · 11 mi
653336b
Houstonia, MO · 14 mi

Missouri planting zones →

Questions about 65321

What planting zone is ZIP code 65321?

ZIP code 65321 (Blackburn, MO) 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 Blackburn, MO?

The median last spring frost (32 °F) near 65321 is April 17; after May 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Sweet Springs station.

When is the first frost in Blackburn, MO?

The median first fall frost near 65321 is October 20, giving a median frost-free growing season of 184 days.

When should I plant tomatoes in 65321?

Start tomato seeds indoors around Feb 20 – Mar 6 and set transplants outside around Apr 24 – May 8, one to three weeks after the median last frost.

How much rain and snow does 65321 get?

About 42.6 inches of precipitation a year (NOAA 1991–2020 normals, Blackburn 3.0 Nne station).

How hot do summers get in Blackburn, MO?

The average high peaks at 89 °F in July, with about 37 days a year at 90 °F or more.

What kind of soil does 65321 have?

The USDA soil survey maps Greenton at the center of ZIP 65321: silt loam, somewhat poorly drained, pH about 6.4 (slightly acidic).

Did spring come early in Blackburn, MO in 2026?

Spring leaf-out near 65321 came on Mar 3 in 2026, 15 days earlier than the 1991–2020 average (Mar 18), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Blackburn, MO?

Intermediate onions: the longest day near 65321 is 14 h 55 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 65321 change?

Yes. The 2012 USDA map put 65321 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.