Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 63650 — Ironton, MO

ZIP code 63650 (Ironton, Iron County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 13 and the first fall frost October 21.

Where ZIP 63650 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 13

First frostOct 21

2012 zone6b

Same zone as on the 2012 map. 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 Ironton, 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 Ironton, MO

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 13median — 50% chance of a later frost

Safe for tender plantsApril 30only 10% chance of frost after

First fall frostOctober 21median — 10% chance by Oct 6

Growing season191 daysfrost-free, median

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

From the NOAA station Farmington, MO — 17 miles away, elevation 899 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 63650

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 2 – Mar 16

SpinachSow outdoors · Mar 2 – Mar 23

Broccoli, cabbageStart indoors · Feb 2 – Feb 16

Broccoli, cabbageTransplant · Mar 23 – Apr 6

Onion setsPlant outdoors · Mar 16 – Mar 30

PotatoesPlant outdoors · Mar 23 – Apr 6

LettuceSow outdoors · Mar 16 – Mar 30

Carrots, beetsSow outdoors · Mar 23 – Apr 6

TomatoesStart indoors · Feb 16 – Mar 2

TomatoesTransplant · Apr 20 – May 4

Peppers, eggplantStart indoors · Feb 2 – Feb 16

Peppers, eggplantTransplant · Apr 27 – May 11

BeansSow outdoors · Apr 20 – May 4

Sweet cornSow outdoors · Apr 20 – May 4

Cucumbers, squashSow outdoors · Apr 20 – May 4

Fall lettuce, spinachSow outdoors · Aug 26 – Sep 9

GarlicPlant cloves · Oct 7 – Nov 11

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 13) and first fall frost (Oct 21) 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 63650 came on Mar 1 — 9 days earlier than the 1991–2020 average (Mar 10).

average
Mar 102026
Mar 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 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.

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 Ironton, MO.

Soil in Ironton, MO

The soil mapped at the center of ZIP 63650 is Bloomsdale — very gravelly loam, well drained.

TextureVery gravelly loama good balance for most vegetables

pH6.5neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.25%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Bloomsdale very gravelly loam, 0 to 3 percent slopes, frequently flooded.

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 63650; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ironton, MO

Summer high89 °Faverage high, July

Winter low23 °Faverage low, January

Hot days32days a year at 90 °F or more

Freezing nights104nights a year at 32 °F or less

Growing degree days4,114base 50 °F — the season’s usable heat

Longest day14 h 46 mindaylight on June 21

Shortest day9 h 34 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation46.2 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Farmington, MO (17 mi away); precipitation: Bismarck 1.3 S, MO (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

636636b

Pilot Knob, MO · 1 mi

636566b

Middle Brook, MO · 9 mi

Caledonia, MO · 13 mi

636486b

Irondale, MO · 15 mi

636516b

Knob Lick, MO · 15 mi

Missouri planting zones →

Questions about 63650

What planting zone is ZIP code 63650?

ZIP code 63650 (Ironton, 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 Ironton, MO?

The median last spring frost (32 °F) near 63650 is April 13; after April 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Farmington station.

When is the first frost in Ironton, MO?

The median first fall frost near 63650 is October 21, giving a median frost-free growing season of 191 days.

When should I plant tomatoes in 63650?

Start tomato seeds indoors around Feb 16 – Mar 2 and set transplants outside around Apr 20 – May 4, one to three weeks after the median last frost.

How much rain and snow does 63650 get?

About 46.2 inches of precipitation a year (NOAA 1991–2020 normals, Bismarck 1.3 S station).

How hot do summers get in Ironton, MO?

The average high peaks at 89 °F in July, with about 32 days a year at 90 °F or more.

What kind of soil does 63650 have?

The USDA soil survey maps Bloomsdale at the center of ZIP 63650: very gravelly loam, well drained, pH about 6.5 (neutral).

Did spring come early in Ironton, MO in 2026?

Spring leaf-out near 63650 came on Mar 1 in 2026, 9 days earlier than the 1991–2020 average (Mar 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ironton, MO?

Intermediate onions: the longest day near 63650 is 14 h 46 min, so day-neutral types bulb best; long-day varieties may not bulb fully.