What USDA hardiness zone is Rosebud County, Montana?

Rosebud County, Montana spans USDA hardiness zones 4a to 5a. 67% of its ZIP codes are zone 4b, so there is no single zone for the county.

When is the last spring frost in Rosebud County, Montana?

The median last spring freeze runs May 8 – May 23 across the 6 NOAA weather stations serving Rosebud County, Montana, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Montana

Planting zones in Rosebud County, Montana

This county spans USDA zones 4a to 5a, so there is no single zone for Rosebud County and anyone who gives you one is rounding. 67% of its ZIP codes are zone 4b; the rest are not.

USDA zones 4a–5a 3 zones across 9 ZIP codes

ZIP codes 9 9 have a NOAA station within range

Weather stations 6 NOAA 1991–2020 normals, across 5,008 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Rosebud County, Montana 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 Rosebud County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 15 – September 30 across the 6 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around March 13 – March 28 — counted back from a last spring freeze of May 8 – May 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 6 stations agreeAt least one station

Every one of the 6 NOAA stations serving this county counts May 23 – September 15 as growing season (115 days). Widening to any single station gives May 8 – September 30 (145 days).

That is a 30-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

Rosebud County covers 3 hardiness zones. A guide that gives the county one zone has picked whichever is largest and rounded everyone else into it — fine for the 67% in zone 4b and wrong for the other 33%. Here is the actual split.

Zone	ZIP codes	Share
4b	6	67%
5a	2	22%
4a	1	11%

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 8 – May 23

First fall freeze September 15 – September 30

Across the 6 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 113–144 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 81.3–84.9 °F in June–August. Summer rain over the same months runs 4.5–5.4" across those 6 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 38% 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 85 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Rosebud 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
59012	4b	Busby, MT	35.4 km
59039	4b	Ingomar 9 E, MT	15.2 km
59043	5a	Busby, MT	22.1 km
59054	4b	Melstone, MT	10.6 km
59083	4b	Melstone, MT	24.1 km
59323	5a	Colstrip, MT	7.3 km
59327	4b	Forsyth, MT	4.0 km
59333	4a	Miles City F Wiley FLD, MT	29.2 km
59347	4b	Forsyth, MT	28.9 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 Rosebud County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 6 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	March 13 – March 28	8 wk before
🌶️ Peppers	Start indoors	March 13 – March 28	8 wk before
🥦 Broccoli	Start indoors	March 27 – April 11	6 wk before
🥬 Cabbage	Start indoors	March 27 – April 11	6 wk before
🥬 Collards	Start indoors	March 27 – April 11	6 wk before
🥬 Kale	Start indoors	March 27 – April 11	6 wk before
🥬 Leaf Lettuce	Start indoors	March 27 – April 11	6 wk before
🫛 Peas	Direct sow	March 27 – April 11	6 wk before
🥬 Spinach	Direct sow	March 27 – April 11	6 wk before
🍠 Sweet Potato	Start indoors	March 27 – April 11	6 wk before
🍅 Tomatoes	Start indoors	March 27 – April 11	6 wk before
🥬 Bok Choy	Start indoors	April 3 – April 18	5 wk before
🥬 Kohlrabi	Start indoors	April 3 – April 18	5 wk before
🥬 Swiss Chard	Start indoors	April 3 – April 18	5 wk before
🥬 Arugula	Direct sow	April 10 – April 25	4 wk before
🥬 Baby Salad Greens	Direct sow	April 10 – April 25	4 wk before
🥕 Beets	Direct sow	April 10 – April 25	4 wk before
🧅 Green Onions	Direct sow	April 10 – April 25	4 wk before
🥬 Mustard Greens	Direct sow	April 10 – April 25	4 wk before
🌶️ Okra	Start indoors	April 10 – April 25	4 wk before
🌱 Radishes	Direct sow	April 10 – April 25	4 wk before
🥔 Turnips	Direct sow	April 10 – April 25	4 wk before
🥬 Cabbage	Set out	April 17 – May 2	3 wk before
🥕 Carrots	Direct sow	April 17 – May 2	3 wk before
🥬 Collards	Direct sow	April 17 – May 2	3 wk before
🥬 Collards	Set out	April 17 – May 2	3 wk before
🥒 Cucumbers	Start indoors	April 17 – May 2	3 wk before
🧅 Green Onions	Set out	April 17 – May 2	3 wk before
🥬 Kale	Direct sow	April 17 – May 2	3 wk before
🥬 Kale	Set out	April 17 – May 2	3 wk before
🥬 Kohlrabi	Direct sow	April 17 – May 2	3 wk before
🥬 Kohlrabi	Set out	April 17 – May 2	3 wk before
🥬 Leaf Lettuce	Direct sow	April 17 – May 2	3 wk before
🎃 Pumpkins	Start indoors	April 17 – May 2	3 wk before
🎃 Summer Squash	Start indoors	April 17 – May 2	3 wk before
🎃 Winter Squash	Start indoors	April 17 – May 2	3 wk before
🥒 Zucchini	Start indoors	April 17 – May 2	3 wk before
🥬 Bok Choy	Direct sow	April 24 – May 9	2 wk before
🥬 Bok Choy	Set out	April 24 – May 9	2 wk before
🥦 Broccoli	Set out	April 24 – May 9	2 wk before
🌿 Cilantro	Direct sow	April 24 – May 9	2 wk before
🥬 Leaf Lettuce	Set out	April 24 – May 9	2 wk before
🥬 Swiss Chard	Direct sow	April 24 – May 9	2 wk before
🥬 Swiss Chard	Set out	April 24 – May 9	2 wk before
🌿 Dill	Direct sow	May 1 – May 16	1 wk before
🫘 Bush Beans	Direct sow	May 15 – May 30	1 wk after
🥒 Cucumbers	Set out	May 15 – May 30	1 wk after
🎃 Pumpkins	Direct sow	May 15 – May 30	1 wk after
🎃 Pumpkins	Set out	May 15 – May 30	1 wk after
🎃 Summer Squash	Direct sow	May 15 – May 30	1 wk after
🎃 Summer Squash	Set out	May 15 – May 30	1 wk after
🌽 Sweet Corn	Direct sow	May 15 – May 30	1 wk after
🍅 Tomatoes	Set out	May 15 – May 30	1 wk after
🎃 Winter Squash	Direct sow	May 15 – May 30	1 wk after
🎃 Winter Squash	Set out	May 15 – May 30	1 wk after
🥒 Zucchini	Direct sow	May 15 – May 30	1 wk after
🥒 Zucchini	Set out	May 15 – May 30	1 wk after
🥒 Cucumbers	Direct sow	May 22 – June 6	2 wk after
🌶️ Okra	Direct sow	May 22 – June 6	2 wk after
🌶️ Okra	Set out	May 22 – June 6	2 wk after
🌶️ Peppers	Set out	May 22 – June 6	2 wk after
🫘 Southern Peas	Direct sow	May 22 – June 6	2 wk after
🍠 Sweet Potato	Set out	May 22 – June 6	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 Rosebud 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 7 to be careful. Median May 8 – May 23 across 6 stations; April 26 is the optimistic end.
First fall freeze: Plan to September 1 to be careful. Median September 15 – September 30 across 6 stations; October 14 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 6 stations behind these numbers

All 6 NOAA stations whose normals this page quotes, spanning about 118 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
Busby, MT	USC00241297	May 23	September 15	113 days
Colstrip, MT	USC00241905	May 15	September 30	138 days
Forsyth, MT	USC00243098	May 9	September 29	142 days
Ingomar 9 E, MT	USC00244386	May 21	September 19	120 days
Melstone, MT	USC00245596	May 10	September 29	141 days
Miles City F Wiley FLD, MT	USW00024037	May 8	September 30	144 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

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

More of Montana

Counties with the same zones — 4a–5a

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.