What USDA hardiness zone is Carbon County, Wyoming?

Carbon County, Wyoming spans USDA hardiness zones 4a to 5b. 64% of its ZIP codes are zone 5a, so there is no single zone for the county.

When is the last spring frost in Carbon County, Wyoming?

The median last spring freeze runs May 12 – June 12 across the 8 NOAA weather stations serving Carbon County, Wyoming, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Wyoming

Planting zones in Carbon County, Wyoming

This county spans USDA zones 4a to 5b, so there is no single zone for Carbon County and anyone who gives you one is rounding. 64% of its ZIP codes are zone 5a; the rest are not.

USDA zones 4a–5b 4 zones across 11 ZIP codes

ZIP codes 11 11 have a NOAA station within range

Weather stations 8 NOAA 1991–2020 normals, across 7,898 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Carbon County, Wyoming 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 Carbon County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 7 – October 4 across the 8 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around March 17 – April 17 — counted back from a last spring freeze of May 12 – June 12 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 8 stations agreeAt least one station

Every one of the 8 NOAA stations serving this county counts June 12 – September 7 as growing season (87 days). Widening to any single station gives May 12 – October 4 (145 days).

That is a 58-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.

Which zone you are in depends where you are

Carbon County covers 4 hardiness zones. A guide that gives the county one zone has picked whichever is largest and rounded everyone else into it — fine for the 64% in zone 5a and wrong for the other 36%. Here is the actual split.

Zone	ZIP codes	Share
5a	7	64%
4b	2	18%
4a	1	9%
5b	1	9%

Zones are published per ZIP code, so yours is exact even though the county's is not. The hardiness tool will tell you which one you are in.

Your freeze dates

Last spring freeze May 12 – June 12

First fall freeze September 7 – October 4

Across the 8 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 83–143 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 78.6–85.4 °F in June–August. Summer rain over the same months runs 2.3–3.5" across those 7 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 24% of it, so a summer garden here is watered rather than rained on. The inches are NOAA's published normals; the inch a week is a rule of thumb, and it takes no account of a 81 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Carbon 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
82301	5a	Rawlins 1N, WY	28.0 km
82321	4b	Baggs, WY	6.1 km
82323	4b	Baggs, WY	11.5 km
82324	5a	Elk Mtn, WY	3.3 km
82325	5a	Saratoga, WY	33.5 km
82327	5a	Leo 6 SW, WY	19.5 km
82329	4a	Medicine Bow, WY	18.2 km
82331	5a	Saratoga, WY	6.0 km
82332	5b	Baggs, WY	30.0 km
82334	5a	Seminoe Rsvr Usbr, WY	23.1 km
82335	5a	Saratoga 4N, WY	28.7 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 Carbon County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 8 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	March 17 – April 17	8 wk before
🌶️ Peppers	Start indoors	March 17 – April 17	8 wk before
🥦 Broccoli	Start indoors	March 31 – May 1	6 wk before
🥬 Cabbage	Start indoors	March 31 – May 1	6 wk before
🥬 Collards	Start indoors	March 31 – May 1	6 wk before
🥬 Kale	Start indoors	March 31 – May 1	6 wk before
🥬 Leaf Lettuce	Start indoors	March 31 – May 1	6 wk before
🫛 Peas	Direct sow	March 31 – May 1	6 wk before
🥬 Spinach	Direct sow	March 31 – May 1	6 wk before
🍠 Sweet Potato	Start indoors	March 31 – May 1	6 wk before
🍅 Tomatoes	Start indoors	March 31 – May 1	6 wk before
🥬 Bok Choy	Start indoors	April 7 – May 8	5 wk before
🥬 Kohlrabi	Start indoors	April 7 – May 8	5 wk before
🥬 Swiss Chard	Start indoors	April 7 – May 8	5 wk before
🥬 Arugula	Direct sow	April 14 – May 15	4 wk before
🥬 Baby Salad Greens	Direct sow	April 14 – May 15	4 wk before
🥕 Beets	Direct sow	April 14 – May 15	4 wk before
🧅 Green Onions	Direct sow	April 14 – May 15	4 wk before
🥬 Mustard Greens	Direct sow	April 14 – May 15	4 wk before
🌶️ Okra	Start indoors	April 14 – May 15	4 wk before
🌱 Radishes	Direct sow	April 14 – May 15	4 wk before
🥔 Turnips	Direct sow	April 14 – May 15	4 wk before
🥬 Cabbage	Set out	April 21 – May 22	3 wk before
🥕 Carrots	Direct sow	April 21 – May 22	3 wk before
🥬 Collards	Direct sow	April 21 – May 22	3 wk before
🥬 Collards	Set out	April 21 – May 22	3 wk before
🥒 Cucumbers	Start indoors	April 21 – May 22	3 wk before
🧅 Green Onions	Set out	April 21 – May 22	3 wk before
🥬 Kale	Direct sow	April 21 – May 22	3 wk before
🥬 Kale	Set out	April 21 – May 22	3 wk before
🥬 Kohlrabi	Direct sow	April 21 – May 22	3 wk before
🥬 Kohlrabi	Set out	April 21 – May 22	3 wk before
🥬 Leaf Lettuce	Direct sow	April 21 – May 22	3 wk before
🎃 Pumpkins	Start indoors	April 21 – May 22	3 wk before
🎃 Summer Squash	Start indoors	April 21 – May 22	3 wk before
🎃 Winter Squash	Start indoors	April 21 – May 22	3 wk before
🥒 Zucchini	Start indoors	April 21 – May 22	3 wk before
🥬 Bok Choy	Direct sow	April 28 – May 29	2 wk before
🥬 Bok Choy	Set out	April 28 – May 29	2 wk before
🥦 Broccoli	Set out	April 28 – May 29	2 wk before
🌿 Cilantro	Direct sow	April 28 – May 29	2 wk before
🥬 Leaf Lettuce	Set out	April 28 – May 29	2 wk before
🥬 Swiss Chard	Direct sow	April 28 – May 29	2 wk before
🥬 Swiss Chard	Set out	April 28 – May 29	2 wk before
🌿 Dill	Direct sow	May 5 – June 5	1 wk before
🫘 Bush Beans	Direct sow	May 19 – June 19	1 wk after
🥒 Cucumbers	Set out	May 19 – June 19	1 wk after
🎃 Pumpkins	Direct sow	May 19 – June 19	1 wk after
🎃 Pumpkins	Set out	May 19 – June 19	1 wk after
🎃 Summer Squash	Direct sow	May 19 – June 19	1 wk after
🎃 Summer Squash	Set out	May 19 – June 19	1 wk after
🌽 Sweet Corn	Direct sow	May 19 – June 19	1 wk after
🍅 Tomatoes	Set out	May 19 – June 19	1 wk after
🎃 Winter Squash	Direct sow	May 19 – June 19	1 wk after
🎃 Winter Squash	Set out	May 19 – June 19	1 wk after
🥒 Zucchini	Direct sow	May 19 – June 19	1 wk after
🥒 Zucchini	Set out	May 19 – June 19	1 wk after
🥒 Cucumbers	Direct sow	May 26 – June 26	2 wk after
🌶️ Okra	Direct sow	May 26 – June 26	2 wk after
🌶️ Okra	Set out	May 26 – June 26	2 wk after
🌶️ Peppers	Set out	May 26 – June 26	2 wk after
🫘 Southern Peas	Direct sow	May 26 – June 26	2 wk after
🍠 Sweet Potato	Set out	May 26 – June 26	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 survives the winter changes across Carbon County

Zone 5a carries 48 of 74 perennial edibles; zone 4a carries 34. The best number is not always the warmest zone — the count peaks in the middle and falls both ways, because the warm end loses plants to insufficient winter chill and summer heat, not to cold.

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 June 30 to be careful. Median May 12 – June 12 across 8 stations; May 1 is the optimistic end.
First fall freeze: Plan to August 12 to be careful. Median September 7 – October 4 across 8 stations; October 17 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 8 stations behind these numbers

All 8 NOAA stations whose normals this page quotes, spanning about 128 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
Baggs, WY	USC00480484	June 1	September 18	108 days
Elk Mtn, WY	USC00482995	May 28	September 13	108 days
Leo 6 SW, WY	USC00485525	May 20	September 28	128 days
Medicine Bow, WY	USC00486120	June 1	September 8	97 days
Rawlins 1N, WY	USC00487529	May 17	October 2	138 days
Saratoga 4N, WY	USC00487995	June 12	September 7	83 days
Saratoga, WY	USC00487990	June 2	September 12	101 days
Seminoe Rsvr Usbr, WY	USC00488074	May 12	October 4	143 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

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

More of Wyoming

Counties with the same zones — 4a–5b

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 4a 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 4a, 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.