What USDA hardiness zone is Clark County, Missouri?

Every ZIP code in Clark County, Missouri is USDA hardiness zone 6a, from the USDA 2023 Plant Hardiness Zone Map.

When is the last spring frost in Clark County, Missouri?

The median last spring freeze runs April 10 – April 23 across the 4 NOAA weather stations serving Clark County, Missouri, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Missouri

Planting zones in Clark County, Missouri

Every ZIP code in this county is USDA zone 6a — so unlike most of the places people look up, there is one right answer here and it holds wherever you are in the county.

USDA zone 6a The same in all 7 ZIP codes

ZIP codes 7 7 have a NOAA station within range

Weather stations 4 NOAA 1991–2020 normals, across 505 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Clark County, Missouri as a whole. Hardiness zones and freeze dates are published per ZIP code, so yours is exact — enter it and this page will tell you your zone, which NOAA station it comes from and how far away that station is.

The growing season in Clark County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives October 17 – October 27 across the 4 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around February 13 – February 26 — counted back from a last spring freeze of April 10 – April 23 here.

Every spring date for your ZIP →

These are ranges across the whole county. The ZIP lookup above gives the dates from your own nearest station instead.

All 4 stations agreeAt least one station

Every one of the 4 NOAA stations serving this county counts April 23 – October 17 as growing season (177 days). Widening to any single station gives April 10 – October 27 (200 days).

That is a 23-day difference inside one county — which is why this page gives ranges rather than a single planting date. The ZIP lookup above resolves it to one station.

Your freeze dates

Last spring freeze April 10 – April 23

First fall freeze October 17 – October 27

Across the 4 NOAA stations serving this county. These are medians — half of years freeze later than the date shown — so treat the later end of each range as the cautious one.

The growing season runs 176–198 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 83.1–84.9 °F in June–August. Summer rain over the same months runs 12.8–13.1" across those 4 stations, against the rough inch a week — about 13 inches over the same 92 days — that a vegetable garden is usually reckoned to want. The middle station covers about 99% of it, so expect to make up the rest. The inches are NOAA's published normals; the inch a week is a rule of thumb, and it takes no account of a 84 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Clark County

Zones are published per ZIP code, not per county, so this is the exact answer rather than the county's average. The station column is the nearest one to that ZIP code's centroid and how far away it is — the same figure the tools use, shown here so you can see which ZIP codes are well covered and which are reaching.

ZIP code	USDA zone	Nearest NOAA station	Distance
63430	6a	Keokuk Lock Dam 19, IA	13.1 km
63445	6a	Keokuk Lock Dam 19, IA	29.5 km
63453	6a	Memphis, MO	27.2 km
63465	6a	Donnellson, IA	16.4 km
63466	6a	Canton L&D 20, MO	16.2 km
63472	6a	Keokuk Lock Dam 19, IA	17.2 km
63474	6a	Memphis, MO	27.2 km

ZIP-code positions are area centroids, so a large rural ZIP code's listed distance is measured from the middle of its area rather than from any particular address in it.

When to start seeds in Clark County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 4 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	February 13 – February 26	8 wk before
🌶️ Peppers	Start indoors	February 13 – February 26	8 wk before
🥦 Broccoli	Start indoors	February 27 – March 12	6 wk before
🥬 Cabbage	Start indoors	February 27 – March 12	6 wk before
🥬 Collards	Start indoors	February 27 – March 12	6 wk before
🥬 Kale	Start indoors	February 27 – March 12	6 wk before
🥬 Leaf Lettuce	Start indoors	February 27 – March 12	6 wk before
🫛 Peas	Direct sow	February 27 – March 12	6 wk before
🥬 Spinach	Direct sow	February 27 – March 12	6 wk before
🍠 Sweet Potato	Start indoors	February 27 – March 12	6 wk before
🍅 Tomatoes	Start indoors	February 27 – March 12	6 wk before
🥬 Bok Choy	Start indoors	March 6 – March 19	5 wk before
🥬 Kohlrabi	Start indoors	March 6 – March 19	5 wk before
🥬 Swiss Chard	Start indoors	March 6 – March 19	5 wk before
🥬 Arugula	Direct sow	March 13 – March 26	4 wk before
🥬 Baby Salad Greens	Direct sow	March 13 – March 26	4 wk before
🥕 Beets	Direct sow	March 13 – March 26	4 wk before
🧅 Green Onions	Direct sow	March 13 – March 26	4 wk before
🥬 Mustard Greens	Direct sow	March 13 – March 26	4 wk before
🌶️ Okra	Start indoors	March 13 – March 26	4 wk before
🌱 Radishes	Direct sow	March 13 – March 26	4 wk before
🥔 Turnips	Direct sow	March 13 – March 26	4 wk before
🥬 Cabbage	Set out	March 20 – April 2	3 wk before
🥕 Carrots	Direct sow	March 20 – April 2	3 wk before
🥬 Collards	Direct sow	March 20 – April 2	3 wk before
🥬 Collards	Set out	March 20 – April 2	3 wk before
🥒 Cucumbers	Start indoors	March 20 – April 2	3 wk before
🧅 Green Onions	Set out	March 20 – April 2	3 wk before
🥬 Kale	Direct sow	March 20 – April 2	3 wk before
🥬 Kale	Set out	March 20 – April 2	3 wk before
🥬 Kohlrabi	Direct sow	March 20 – April 2	3 wk before
🥬 Kohlrabi	Set out	March 20 – April 2	3 wk before
🥬 Leaf Lettuce	Direct sow	March 20 – April 2	3 wk before
🎃 Pumpkins	Start indoors	March 20 – April 2	3 wk before
🎃 Summer Squash	Start indoors	March 20 – April 2	3 wk before
🎃 Winter Squash	Start indoors	March 20 – April 2	3 wk before
🥒 Zucchini	Start indoors	March 20 – April 2	3 wk before
🥬 Bok Choy	Direct sow	March 27 – April 9	2 wk before
🥬 Bok Choy	Set out	March 27 – April 9	2 wk before
🥦 Broccoli	Set out	March 27 – April 9	2 wk before
🌿 Cilantro	Direct sow	March 27 – April 9	2 wk before
🥬 Leaf Lettuce	Set out	March 27 – April 9	2 wk before
🥬 Swiss Chard	Direct sow	March 27 – April 9	2 wk before
🥬 Swiss Chard	Set out	March 27 – April 9	2 wk before
🌿 Dill	Direct sow	April 3 – April 16	1 wk before
🫘 Bush Beans	Direct sow	April 17 – April 30	1 wk after
🥒 Cucumbers	Set out	April 17 – April 30	1 wk after
🎃 Pumpkins	Direct sow	April 17 – April 30	1 wk after
🎃 Pumpkins	Set out	April 17 – April 30	1 wk after
🎃 Summer Squash	Direct sow	April 17 – April 30	1 wk after
🎃 Summer Squash	Set out	April 17 – April 30	1 wk after
🌽 Sweet Corn	Direct sow	April 17 – April 30	1 wk after
🍅 Tomatoes	Set out	April 17 – April 30	1 wk after
🎃 Winter Squash	Direct sow	April 17 – April 30	1 wk after
🎃 Winter Squash	Set out	April 17 – April 30	1 wk after
🥒 Zucchini	Direct sow	April 17 – April 30	1 wk after
🥒 Zucchini	Set out	April 17 – April 30	1 wk after
🥒 Cucumbers	Direct sow	April 24 – May 7	2 wk after
🌶️ Okra	Direct sow	April 24 – May 7	2 wk after
🌶️ Okra	Set out	April 24 – May 7	2 wk after
🌶️ Peppers	Set out	April 24 – May 7	2 wk after
🫘 Southern Peas	Direct sow	April 24 – May 7	2 wk after
🍠 Sweet Potato	Set out	April 24 – May 7	2 wk after

Offsets are published guidance; the dates they land on are computed from measured NOAA normals. The seed-starting tool does this for your own ZIP code and counts the days.

What lives through a zone 6a winter

Of 74 perennial edibles, 51 come through a zone 6a winter — and 0 fail here for being too warm rather than too cold, needing more winter chill than this county gets or more heat than they tolerate. Among the ones that work: Cranberry, Honeyberry, Lingonberry, Apple, Aronia, Black Currant, Elderberry, Gooseberry.

Hardiness ranges are a judgement, published by growers rather than measured; the zone they are compared against is measured. On a warm-end verdict, check with your local extension service — a coastal zone 8 and an inland zone 8 are not the same summer.

Cautious — shortens the seasonMedian across stationsOptimistic

Last spring freeze: Plan to May 6 to be careful. Median April 10 – April 23 across 4 stations; March 29 is the optimistic end.
First fall freeze: Plan to October 2 to be careful. Median October 17 – October 27 across 4 stations; November 7 is the optimistic end.

NOAA publishes these as probabilities, not averages — the middle figure is a median, so half of years fall either side of it. The cautious end is the 10% tail: in roughly nine years in ten the freeze falls on the safe side of it.

The 4 stations behind these numbers

All 4 NOAA stations whose normals this page quotes, spanning about 56 km north to south. Every one is named with its identifier in the station list below — this page does not single one out, because no one station speaks for a whole county.

A relative sketch, not a map with a projection: longitude is adjusted for latitude so the shape is not stretched, and there is no basemap. For the one station nearest a specific address, with its real distance, use the ZIP lookup above.

These are the stations this county's ZIP codes actually cite as nearest — not a claim that each one sits inside its boundary, since a rural ZIP legitimately reaches over it. Every figure above comes from them, and each is named so you can check it.

Station	NOAA ID	Last spring freeze	First fall freeze	Season
Canton L&D 20, MO	USC00231275	April 11	October 23	194 days
Donnellson, IA	USC00132299	April 17	October 22	187 days
Keokuk Lock Dam 19, IA	USC00134381	April 10	October 27	198 days
Memphis, MO	USC00235492	April 23	October 17	176 days

These are medians, not averages — NOAA publishes freeze dates as a probability distribution, and half of years freeze later than the date shown.

Your own ZIP

Work out your own dates

This page describes a whole county. Every tool below answers for one ZIP code, which is the grain the underlying data is published at.

Other places to compare

Clark County sits in Missouri. That page carries the whole state's zone spread, its metro areas, and every other county in it with a page here.

More of Missouri

Counties with the same zones — 6a

Matched on the exact zone set, not a dominant zone, so the winter answer on these pages really is the same one as here.

Gear

If you want to act on this

Each link opens an Amazon search rather than a product we picked. We have not tested these and do not rank them — the search is the honest version, and you choose.

Trunk wrapZone 6a is cold enough that winter sun on a young trunk does more damage than the cold does.
Row cover and frost clothThe season here closes at the first fall freeze dated above — a cover buys back some of those days at the end.
MulchFor the perennials nearest their cold limit in zone 6a, where an insulated crown is what decides whether they come back.

As an Amazon Associate we earn from qualifying purchases. That costs you nothing extra, and it buys no influence over anything on this site: the dates come from NOAA normals and the zones from the USDA, and no product affects either.

Sources

Where these numbers come from

Hardiness zones are the USDA 2023 Plant Hardiness Zone Map, published per ZIP code by PRISM at Oregon State. Freeze dates and growing-season lengths are NOAA 1991–2020 Climate Normals, taken per station and cited above by name and NOAA ID.

County boundaries come from the Census ZCTA-to-county relation, which is what places each ZIP code — and which treats parishes, boroughs and census areas as county equivalents. No station is chosen to represent this county: every range above is taken across all of them and the count is stated, because picking one would be a judgement dressed as a measurement.