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

Planting zone for 63301 — Saint Charles, MO

ZIP code 63301 (Saint Charles, Saint Charles County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 8 and the first fall frost October 29.

Where ZIP 63301 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 8

First frostOct 29

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 Saint Charles, 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 Saint Charles, MO

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 8median — 50% chance of a later frost

Safe for tender plantsApril 24only 10% chance of frost after

First fall frostOctober 29median — 10% chance by Oct 16

Growing season203 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 30 and returns around November 10.

From the NOAA station St Charles Elm Pt, MO — 4 miles away, elevation 472 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 63301

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 25 – Mar 11

SpinachSow outdoors · Feb 25 – Mar 18

Broccoli, cabbageStart indoors · Jan 28 – Feb 11

Broccoli, cabbageTransplant · Mar 18 – Apr 1

Onion setsPlant outdoors · Mar 11 – Mar 25

PotatoesPlant outdoors · Mar 18 – Apr 1

LettuceSow outdoors · Mar 11 – Mar 25

Carrots, beetsSow outdoors · Mar 18 – Apr 1

TomatoesStart indoors · Feb 11 – Feb 25

TomatoesTransplant · Apr 15 – Apr 29

Peppers, eggplantStart indoors · Jan 28 – Feb 11

Peppers, eggplantTransplant · Apr 22 – May 6

BeansSow outdoors · Apr 15 – Apr 29

Sweet cornSow outdoors · Apr 15 – Apr 29

Cucumbers, squashSow outdoors · Apr 15 – Apr 29

Fall lettuce, spinachSow outdoors · Sep 3 – Sep 17

GarlicPlant cloves · Oct 15 – Nov 19

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 8) and first fall frost (Oct 29) 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 63301 came on Mar 6 — 11 days earlier than the 1991–2020 average (Mar 17).

average
Mar 172026
Mar 6

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 Saint Charles, MO.

Soil in Saint Charles, MO

The soil mapped at the center of ZIP 63301 is DeSioux — loam, well drained.

TextureLoama good balance for most vegetables

pH6.6neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2.55%moderate

Hydrologic groupBwater soaks in moderately

Farmland classprime farmlandUSDA classification

Map unit: DeSioux loam, 0 to 2 percent slopes, rarely 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 63301; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Saint Charles, MO

Summer high88 °Faverage high, July

Winter low22 °Faverage low, January

Hot days34days a year at 90 °F or more

Freezing nights105nights a year at 32 °F or less

Growing degree days4,108base 50 °F — the season’s usable heat

Longest day14 h 54 mindaylight on June 21

Shortest day9 h 26 mindaylight on December 21

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

Precipitation45.7 inper year, rain and melted snow

Snowfall9 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: St Charles Elm Pt, MO (4 mi away); precipitation: St Charles Elm Pt, MO (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

633027a

Saint Charles, MO · 5 mi

630456b

Earth City, MO · 6 mi

630446b

Bridgeton, MO · 6 mi

633736b

Portage Des Sioux, MO · 6 mi

630317a

Florissant, MO · 7 mi

630427a

Hazelwood, MO · 7 mi

620366b

Golden Eagle, IL · 8 mi

633466b

Flinthill, MO · 8 mi

All 4 ZIP codes in Saint Charles → · Missouri planting zones →

Questions about 63301

What planting zone is ZIP code 63301?

ZIP code 63301 (Saint Charles, 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 Saint Charles, MO?

The median last spring frost (32 °F) near 63301 is April 8; after April 24 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, St Charles Elm Pt station.

When is the first frost in Saint Charles, MO?

The median first fall frost near 63301 is October 29, giving a median frost-free growing season of 203 days.

When should I plant tomatoes in 63301?

Start tomato seeds indoors around Feb 11 – Feb 25 and set transplants outside around Apr 15 – Apr 29, one to three weeks after the median last frost.

How much rain and snow does 63301 get?

About 45.7 inches of precipitation a year and 9 inches of snowfall (NOAA 1991–2020 normals, St Charles Elm Pt station).

How hot do summers get in Saint Charles, MO?

The average high peaks at 88 °F in July, with about 34 days a year at 90 °F or more.

What kind of soil does 63301 have?

The USDA soil survey maps DeSioux at the center of ZIP 63301: loam, well drained, pH about 6.6 (neutral).

Did spring come early in Saint Charles, MO in 2026?

Spring leaf-out near 63301 came on Mar 6 in 2026, 11 days earlier than the 1991–2020 average (Mar 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Saint Charles, MO?

Intermediate onions: the longest day near 63301 is 14 h 54 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 63301 change?

Yes. The 2012 USDA map put 63301 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.