What USDA hardiness zone is Carter County, Oklahoma?

Every ZIP code in Carter County, Oklahoma is USDA hardiness zone 8a, from the USDA 2023 Plant Hardiness Zone Map.

When is the last spring frost in Carter County, Oklahoma?

The median last spring freeze runs March 18 – April 6 across the 4 NOAA weather stations serving Carter County, Oklahoma, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Oklahoma

Planting zones in Carter County, Oklahoma

Every ZIP code in this county is USDA zone 8a — 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 8a The same in all 12 ZIP codes

ZIP codes 12 12 have a NOAA station within range

Weather stations 4 NOAA 1991–2020 normals, across 822 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Carter County, Oklahoma 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 Carter County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives November 1 – November 10 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 January 21 – February 9 — counted back from a last spring freeze of March 18 – April 6 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 6 – November 1 as growing season (209 days). Widening to any single station gives March 18 – November 10 (237 days).

That is a 28-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 March 18 – April 6

First fall freeze November 1 – November 10

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 204–238 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 92.4–92.8 °F in June–August. That is past the point where tomato and pepper pollen fails and cool-season greens bolt, so in this county heat decides as much as frost does. Summer rain over the same months runs 9.4–10.3" across those 2 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 79% 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 93 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Carter 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
73401	8a	Ardmore 3Ene Mesonet, OK	2.6 km
73435	8a	Healdton 3 E, OK	15.5 km
73436	8a	Ardmore 3Ene Mesonet, OK	11.2 km
73437	8a	Healdton 3 E, OK	15.0 km
73438	8a	Healdton 3 E, OK	9.3 km
73443	8a	Ardmore 7Wnw Mesonet, OK	11.5 km
73444	8a	Healdton 3 E, OK	27.0 km
73458	8a	Healdton 3 E, OK	16.2 km
73463	8a	Healdton 3 E, OK	12.3 km
73481	8a	Healdton 3 E, OK	23.7 km
73487	8a	Healdton 3 E, OK	26.3 km
73488	8a	Velma 7Nw Mesonet, OK	19.6 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 Carter 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	January 21 – February 9	8 wk before
🌶️ Peppers	Start indoors	January 21 – February 9	8 wk before
🥦 Broccoli	Start indoors	February 4 – February 23	6 wk before
🥬 Cabbage	Start indoors	February 4 – February 23	6 wk before
🥬 Collards	Start indoors	February 4 – February 23	6 wk before
🥬 Kale	Start indoors	February 4 – February 23	6 wk before
🥬 Leaf Lettuce	Start indoors	February 4 – February 23	6 wk before
🫛 Peas	Direct sow	February 4 – February 23	6 wk before
🥬 Spinach	Direct sow	February 4 – February 23	6 wk before
🍠 Sweet Potato	Start indoors	February 4 – February 23	6 wk before
🍅 Tomatoes	Start indoors	February 4 – February 23	6 wk before
🥬 Bok Choy	Start indoors	February 11 – March 2	5 wk before
🥬 Kohlrabi	Start indoors	February 11 – March 2	5 wk before
🥬 Swiss Chard	Start indoors	February 11 – March 2	5 wk before
🥬 Arugula	Direct sow	February 18 – March 9	4 wk before
🥬 Baby Salad Greens	Direct sow	February 18 – March 9	4 wk before
🥕 Beets	Direct sow	February 18 – March 9	4 wk before
🧅 Green Onions	Direct sow	February 18 – March 9	4 wk before
🥬 Mustard Greens	Direct sow	February 18 – March 9	4 wk before
🌶️ Okra	Start indoors	February 18 – March 9	4 wk before
🌱 Radishes	Direct sow	February 18 – March 9	4 wk before
🥔 Turnips	Direct sow	February 18 – March 9	4 wk before
🥬 Cabbage	Set out	February 25 – March 16	3 wk before
🥕 Carrots	Direct sow	February 25 – March 16	3 wk before
🥬 Collards	Direct sow	February 25 – March 16	3 wk before
🥬 Collards	Set out	February 25 – March 16	3 wk before
🥒 Cucumbers	Start indoors	February 25 – March 16	3 wk before
🧅 Green Onions	Set out	February 25 – March 16	3 wk before
🥬 Kale	Direct sow	February 25 – March 16	3 wk before
🥬 Kale	Set out	February 25 – March 16	3 wk before
🥬 Kohlrabi	Direct sow	February 25 – March 16	3 wk before
🥬 Kohlrabi	Set out	February 25 – March 16	3 wk before
🥬 Leaf Lettuce	Direct sow	February 25 – March 16	3 wk before
🎃 Pumpkins	Start indoors	February 25 – March 16	3 wk before
🎃 Summer Squash	Start indoors	February 25 – March 16	3 wk before
🎃 Winter Squash	Start indoors	February 25 – March 16	3 wk before
🥒 Zucchini	Start indoors	February 25 – March 16	3 wk before
🥬 Bok Choy	Direct sow	March 4 – March 23	2 wk before
🥬 Bok Choy	Set out	March 4 – March 23	2 wk before
🥦 Broccoli	Set out	March 4 – March 23	2 wk before
🌿 Cilantro	Direct sow	March 4 – March 23	2 wk before
🥬 Leaf Lettuce	Set out	March 4 – March 23	2 wk before
🥬 Swiss Chard	Direct sow	March 4 – March 23	2 wk before
🥬 Swiss Chard	Set out	March 4 – March 23	2 wk before
🌿 Dill	Direct sow	March 11 – March 30	1 wk before
🫘 Bush Beans	Direct sow	March 25 – April 13	1 wk after
🥒 Cucumbers	Set out	March 25 – April 13	1 wk after
🎃 Pumpkins	Direct sow	March 25 – April 13	1 wk after
🎃 Pumpkins	Set out	March 25 – April 13	1 wk after
🎃 Summer Squash	Direct sow	March 25 – April 13	1 wk after
🎃 Summer Squash	Set out	March 25 – April 13	1 wk after
🌽 Sweet Corn	Direct sow	March 25 – April 13	1 wk after
🍅 Tomatoes	Set out	March 25 – April 13	1 wk after
🎃 Winter Squash	Direct sow	March 25 – April 13	1 wk after
🎃 Winter Squash	Set out	March 25 – April 13	1 wk after
🥒 Zucchini	Direct sow	March 25 – April 13	1 wk after
🥒 Zucchini	Set out	March 25 – April 13	1 wk after
🥒 Cucumbers	Direct sow	April 1 – April 20	2 wk after
🌶️ Okra	Direct sow	April 1 – April 20	2 wk after
🌶️ Okra	Set out	April 1 – April 20	2 wk after
🌶️ Peppers	Set out	April 1 – April 20	2 wk after
🫘 Southern Peas	Direct sow	April 1 – April 20	2 wk after
🍠 Sweet Potato	Set out	April 1 – April 20	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 8a winter

Of 74 perennial edibles, 57 come through a zone 8a winter — and 8 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: Apple, Aronia, Elderberry, Summer Raspberry, Asparagus, Horseradish, Rhubarb, Sunchoke.

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 April 25 to be careful. Median March 18 – April 6 across 4 stations; February 28 is the optimistic end.
First fall freeze: Plan to October 15 to be careful. Median November 1 – November 10 across 4 stations; November 28 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 37 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
Ardmore 3Ene Mesonet, OK	USC00340313	March 18	November 10	238 days
Ardmore 7Wnw Mesonet, OK	USC00340312	March 21	November 8	231 days
Healdton 3 E, OK	USC00344001	April 6	November 1	204 days
Velma 7Nw Mesonet, OK	USC00349130	March 28	November 7	227 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

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

More of Oklahoma

Counties with the same zones — 8a

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.

Shade clothSummer highs here average 93 °F, at or above the 90 °F point where lettuce and spinach bolt and tomato pollen fails.
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 8a, 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.