Montana
Planting zones in Garfield County, Montana
This county spans USDA zones 4a to 4b, so there is no single zone for Garfield County and anyone who gives you one is rounding. 50% of its ZIP codes are zone 4a; the rest are not.
Your ZIP code
Get the exact answer for your address
Everything above describes Garfield 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 Garfield County is closing
Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 14 – October 4 across the 5 NOAA stations serving this county .
Your next season already has a date
The first job of it is 🧅 Green Onions, start indoors, around March 10 – March 30 — counted back from a last spring freeze of May 5 – May 25 here.
These are ranges across the whole county. The ZIP lookup above gives the dates from your own nearest station instead.
All 5 stations agreeAt least one station
Every one of the 5 NOAA stations serving this county counts May 25 – September 14 as growing season (112 days). Widening to any single station gives May 5 – October 4 (152 days).
That is a 40-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
Garfield County covers 2 hardiness zones. A guide that gives the county one zone has picked whichever is largest and rounded everyone else into it — fine for the 50% in zone 4a and wrong for the other 50%. Here is the actual split.
| Zone | ZIP codes | Share | |
|---|---|---|---|
| 4a | 3 | 50% | |
| 4b | 3 | 50% |
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
Across the 5 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 110–151 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 82.3–84.1 °F in June–August. Summer rain over the same months runs 5.0–5.9" across those 5 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 40% 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 Garfield 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 |
|---|---|---|---|
| 59058 | 4b | Mosby 4 Ene, MT | 6.1 km |
| 59077 | 4b | Mosby 4 Ene, MT | 30.3 km |
| 59312 | 4a | Rock Springs, MT | 24.2 km |
| 59318 | 4b | Jordan AP, MT | 46.9 km |
| 59322 | 4a | Cohagen, MT | 5.5 km |
| 59337 | 4a | Jordan, MT | 12.4 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 Garfield County
Every date below is anchored on the last spring freeze at each station and reported as a range across all 5 of them, because no one station speaks for the county.
| Crop | Job | When | Offset |
|---|---|---|---|
| 🧅 Green Onions | Start indoors | March 10 – March 30 | 8 wk before |
| 🌶️ Peppers | Start indoors | March 10 – March 30 | 8 wk before |
| 🥦 Broccoli | Start indoors | March 24 – April 13 | 6 wk before |
| 🥬 Cabbage | Start indoors | March 24 – April 13 | 6 wk before |
| 🥬 Collards | Start indoors | March 24 – April 13 | 6 wk before |
| 🥬 Kale | Start indoors | March 24 – April 13 | 6 wk before |
| 🥬 Leaf Lettuce | Start indoors | March 24 – April 13 | 6 wk before |
| 🫛 Peas | Direct sow | March 24 – April 13 | 6 wk before |
| 🥬 Spinach | Direct sow | March 24 – April 13 | 6 wk before |
| 🍠 Sweet Potato | Start indoors | March 24 – April 13 | 6 wk before |
| 🍅 Tomatoes | Start indoors | March 24 – April 13 | 6 wk before |
| 🥬 Bok Choy | Start indoors | March 31 – April 20 | 5 wk before |
| 🥬 Kohlrabi | Start indoors | March 31 – April 20 | 5 wk before |
| 🥬 Swiss Chard | Start indoors | March 31 – April 20 | 5 wk before |
| 🥬 Arugula | Direct sow | April 7 – April 27 | 4 wk before |
| 🥬 Baby Salad Greens | Direct sow | April 7 – April 27 | 4 wk before |
| 🥕 Beets | Direct sow | April 7 – April 27 | 4 wk before |
| 🧅 Green Onions | Direct sow | April 7 – April 27 | 4 wk before |
| 🥬 Mustard Greens | Direct sow | April 7 – April 27 | 4 wk before |
| 🌶️ Okra | Start indoors | April 7 – April 27 | 4 wk before |
| 🌱 Radishes | Direct sow | April 7 – April 27 | 4 wk before |
| 🥔 Turnips | Direct sow | April 7 – April 27 | 4 wk before |
| 🥬 Cabbage | Set out | April 14 – May 4 | 3 wk before |
| 🥕 Carrots | Direct sow | April 14 – May 4 | 3 wk before |
| 🥬 Collards | Direct sow | April 14 – May 4 | 3 wk before |
| 🥬 Collards | Set out | April 14 – May 4 | 3 wk before |
| 🥒 Cucumbers | Start indoors | April 14 – May 4 | 3 wk before |
| 🧅 Green Onions | Set out | April 14 – May 4 | 3 wk before |
| 🥬 Kale | Direct sow | April 14 – May 4 | 3 wk before |
| 🥬 Kale | Set out | April 14 – May 4 | 3 wk before |
| 🥬 Kohlrabi | Direct sow | April 14 – May 4 | 3 wk before |
| 🥬 Kohlrabi | Set out | April 14 – May 4 | 3 wk before |
| 🥬 Leaf Lettuce | Direct sow | April 14 – May 4 | 3 wk before |
| 🎃 Pumpkins | Start indoors | April 14 – May 4 | 3 wk before |
| 🎃 Summer Squash | Start indoors | April 14 – May 4 | 3 wk before |
| 🎃 Winter Squash | Start indoors | April 14 – May 4 | 3 wk before |
| 🥒 Zucchini | Start indoors | April 14 – May 4 | 3 wk before |
| 🥬 Bok Choy | Direct sow | April 21 – May 11 | 2 wk before |
| 🥬 Bok Choy | Set out | April 21 – May 11 | 2 wk before |
| 🥦 Broccoli | Set out | April 21 – May 11 | 2 wk before |
| 🌿 Cilantro | Direct sow | April 21 – May 11 | 2 wk before |
| 🥬 Leaf Lettuce | Set out | April 21 – May 11 | 2 wk before |
| 🥬 Swiss Chard | Direct sow | April 21 – May 11 | 2 wk before |
| 🥬 Swiss Chard | Set out | April 21 – May 11 | 2 wk before |
| 🌿 Dill | Direct sow | April 28 – May 18 | 1 wk before |
| 🫘 Bush Beans | Direct sow | May 12 – June 1 | 1 wk after |
| 🥒 Cucumbers | Set out | May 12 – June 1 | 1 wk after |
| 🎃 Pumpkins | Direct sow | May 12 – June 1 | 1 wk after |
| 🎃 Pumpkins | Set out | May 12 – June 1 | 1 wk after |
| 🎃 Summer Squash | Direct sow | May 12 – June 1 | 1 wk after |
| 🎃 Summer Squash | Set out | May 12 – June 1 | 1 wk after |
| 🌽 Sweet Corn | Direct sow | May 12 – June 1 | 1 wk after |
| 🍅 Tomatoes | Set out | May 12 – June 1 | 1 wk after |
| 🎃 Winter Squash | Direct sow | May 12 – June 1 | 1 wk after |
| 🎃 Winter Squash | Set out | May 12 – June 1 | 1 wk after |
| 🥒 Zucchini | Direct sow | May 12 – June 1 | 1 wk after |
| 🥒 Zucchini | Set out | May 12 – June 1 | 1 wk after |
| 🥒 Cucumbers | Direct sow | May 19 – June 8 | 2 wk after |
| 🌶️ Okra | Direct sow | May 19 – June 8 | 2 wk after |
| 🌶️ Okra | Set out | May 19 – June 8 | 2 wk after |
| 🌶️ Peppers | Set out | May 19 – June 8 | 2 wk after |
| 🫘 Southern Peas | Direct sow | May 19 – June 8 | 2 wk after |
| 🍠 Sweet Potato | Set out | May 19 – June 8 | 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 Garfield County
Zone 4a carries 34 of 74 perennial edibles; zone 4a carries 34.
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 9 to be careful. Median May 5 – May 25 across 5 stations; April 20 is the optimistic end.
- First fall freeze
- Plan to August 31 to be careful. Median September 14 – October 4 across 5 stations; October 19 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 5 stations behind these numbers
All 5 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 |
|---|---|---|---|---|
| Cohagen, MT | USC00241875 | May 25 | September 14 | 110 days |
| Jordan AP, MT | USW00094051 | May 18 | September 20 | 123 days |
| Jordan, MT | USC00244522 | May 21 | September 18 | 118 days |
| Mosby 4 Ene, MT | USC00245872 | May 5 | October 4 | 151 days |
| Rock Springs, MT | USC00247136 | May 15 | September 25 | 132 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
Garfield 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
- Judith Basin County, MT 4b
- Phillips County, MT 3b–4b
- Roosevelt County, MT 4a
- Teton County, MT 4a–4b
- Liberty County, MT 4a
- Pondera County, MT 4a–4b
- Flathead County, MT 4b–6a
- Lake County, MT 5b–6a
- Madison County, MT 4b–5a
- Big Horn County, MT 4b–5a
- Sheridan County, MT 3b–4a
- Valley County, MT 3b–4a
Counties with the same zones — 4a–4b
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.