State guide
Planting zones in Montana
Montana spans USDA zones 3b to 6b across its 368 ZIP codes, so there is no single zone for the state and anyone who gives you one is rounding. 33% of its ZIP codes are zone 4b; the rest are not.
Your ZIP code
Get the exact answer for your address
Everything above describes 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.
Which zone you are in depends where you are
Montana covers 7 hardiness zones. A guide that gives the state one zone has picked whichever is largest and rounded everyone else into it — which is fine for the 33% in zone 4b and wrong for the other 67%. Here is the actual split, by ZIP code.
| Zone | ZIP codes | Share | |
|---|---|---|---|
| 4b | 121 | 33% | |
| 5a | 95 | 26% | |
| 4a | 69 | 19% | |
| 6a | 29 | 8% | |
| 5b | 28 | 8% | |
| 3b | 25 | 7% | |
| 6b | 1 | 0% |
Zones are published per ZIP code, so yours is exact even though the state's is not. The hardiness tool will tell you which one you are in.
Your freeze dates
Those are the earliest and latest medians among the 216 stations in Montana with an ordinary freeze window — not an average, and not one station standing in for the rest. Half of years freeze later than a station's own median.
Your growing season
NOAA publishes a growing-season length for each station, and across the 216 stations in Montana it runs 77–165 days . That figure is published, not computed from the two freeze dates — subtracting one from the other gives the wrong answer wherever a season crosses New Year. Mean summer high (June–August) runs 70–88 °F , below the 90 °F point where cool-season crops reliably bolt.
The ends of each range, named
A range with no station behind it cannot be checked, and Montana has too many stations to table them all. So every figure above is reported here with the station standing at each end of it, by name and NOAA ID. No station on this page represents Montana — these are its edges, which is a different claim.
| Measure | Earliest / lowest | Station | Latest / highest | Station |
|---|---|---|---|---|
| Last spring freeze | April 30 | Norris Madison Pwr House, MT USC00246157 | June 18 | Tizer Gardens, MT USC00248239 |
| First fall freeze | September 2 | Opheim 12 Sse, MT USC00246238 | October 15 | Bigfork 13 S, MT USC00240755 |
| Growing season | 77 days | Lewistown 42 Wsw, MT USW00004140 | 165 days | Bigfork 13 S, MT USC00240755 |
| Mean summer high | 70 °F | St. Mary 1 Ssw, MT USW00004130 | 88 °F | Mizpah 4 Nnw, MT USC00245754 |
These are medians, not averages — NOAA publishes freeze dates as a probability distribution, and half of years freeze later than the date shown.
When to start seeds in Montana
Every spring job for 63 crop dates, counted from this state's own last spring freeze. Each is a range across all 216 stations — the earliest and latest that job falls anywhere in Montana — because no one station speaks for a whole state. The ranges are wide on purpose: that width is the state.
| Crop | Job | When | Offset |
|---|---|---|---|
| Green Onions | Start indoors | March 5 – April 23 | 8 weeks before |
| Peppers | Start indoors | March 5 – April 23 | 8 weeks before |
| Broccoli | Start indoors | March 19 – May 7 | 6 weeks before |
| Cabbage | Start indoors | March 19 – May 7 | 6 weeks before |
| Collards | Start indoors | March 19 – May 7 | 6 weeks before |
| Kale | Start indoors | March 19 – May 7 | 6 weeks before |
| Leaf Lettuce | Start indoors | March 19 – May 7 | 6 weeks before |
| Peas | Direct sow | March 19 – May 7 | 6 weeks before |
| Spinach | Direct sow | March 19 – May 7 | 6 weeks before |
| Sweet Potato | Start indoors | March 19 – May 7 | 6 weeks before |
| Tomatoes | Start indoors | March 19 – May 7 | 6 weeks before |
| Bok Choy | Start indoors | March 26 – May 14 | 5 weeks before |
| Kohlrabi | Start indoors | March 26 – May 14 | 5 weeks before |
| Swiss Chard | Start indoors | March 26 – May 14 | 5 weeks before |
| Arugula | Direct sow | April 2 – May 21 | 4 weeks before |
| Baby Salad Greens | Direct sow | April 2 – May 21 | 4 weeks before |
| Beets | Direct sow | April 2 – May 21 | 4 weeks before |
| Green Onions | Direct sow | April 2 – May 21 | 4 weeks before |
| Mustard Greens | Direct sow | April 2 – May 21 | 4 weeks before |
| Okra | Start indoors | April 2 – May 21 | 4 weeks before |
| Radishes | Direct sow | April 2 – May 21 | 4 weeks before |
| Turnips | Direct sow | April 2 – May 21 | 4 weeks before |
| Cabbage | Set out | April 9 – May 28 | 3 weeks before |
| Carrots | Direct sow | April 9 – May 28 | 3 weeks before |
| Collards | Direct sow | April 9 – May 28 | 3 weeks before |
| Collards | Set out | April 9 – May 28 | 3 weeks before |
| Cucumbers | Start indoors | April 9 – May 28 | 3 weeks before |
| Green Onions | Set out | April 9 – May 28 | 3 weeks before |
| Kale | Direct sow | April 9 – May 28 | 3 weeks before |
| Kale | Set out | April 9 – May 28 | 3 weeks before |
| Kohlrabi | Direct sow | April 9 – May 28 | 3 weeks before |
| Kohlrabi | Set out | April 9 – May 28 | 3 weeks before |
| Leaf Lettuce | Direct sow | April 9 – May 28 | 3 weeks before |
| Pumpkins | Start indoors | April 9 – May 28 | 3 weeks before |
| Summer Squash | Start indoors | April 9 – May 28 | 3 weeks before |
| Winter Squash | Start indoors | April 9 – May 28 | 3 weeks before |
| Zucchini | Start indoors | April 9 – May 28 | 3 weeks before |
| Bok Choy | Direct sow | April 16 – June 4 | 2 weeks before |
| Bok Choy | Set out | April 16 – June 4 | 2 weeks before |
| Broccoli | Set out | April 16 – June 4 | 2 weeks before |
| Cilantro | Direct sow | April 16 – June 4 | 2 weeks before |
| Leaf Lettuce | Set out | April 16 – June 4 | 2 weeks before |
| Swiss Chard | Direct sow | April 16 – June 4 | 2 weeks before |
| Swiss Chard | Set out | April 16 – June 4 | 2 weeks before |
| Dill | Direct sow | April 23 – June 11 | 1 week before |
| Bush Beans | Direct sow | May 7 – June 25 | 1 week after |
| Cucumbers | Set out | May 7 – June 25 | 1 week after |
| Pumpkins | Direct sow | May 7 – June 25 | 1 week after |
| Pumpkins | Set out | May 7 – June 25 | 1 week after |
| Summer Squash | Direct sow | May 7 – June 25 | 1 week after |
| Summer Squash | Set out | May 7 – June 25 | 1 week after |
| Sweet Corn | Direct sow | May 7 – June 25 | 1 week after |
| Tomatoes | Set out | May 7 – June 25 | 1 week after |
| Winter Squash | Direct sow | May 7 – June 25 | 1 week after |
| Winter Squash | Set out | May 7 – June 25 | 1 week after |
| Zucchini | Direct sow | May 7 – June 25 | 1 week after |
| Zucchini | Set out | May 7 – June 25 | 1 week after |
| Cucumbers | Direct sow | May 14 – July 2 | 2 weeks after |
| Okra | Direct sow | May 14 – July 2 | 2 weeks after |
| Okra | Set out | May 14 – July 2 | 2 weeks after |
| Peppers | Set out | May 14 – July 2 | 2 weeks after |
| Southern Peas | Direct sow | May 14 – July 2 | 2 weeks after |
| Sweet Potato | Set out | May 14 – July 2 | 2 weeks after |
The week offsets are conventional extension guidance and vary by variety; the freeze dates they are counted from are measured. For a single date rather than a range, run when do I start my seeds? with your own ZIP code.
What survives the winter changes across Montana
Of 74 perennial fruits, nuts, berries, vegetables and herbs, 51 come through the winter in zone 6a and only 17 in zone 3b. Winter hardiness runs on the zone alone, so each row below is exact for the ZIP codes in it.
| Zone | ZIPs | Survive | Fail for being too warm |
|---|---|---|---|
| 3b | 25 | 17 of 74 | 0 |
| 4a | 69 | 34 of 74 | 0 |
| 4b | 121 | 34 of 74 | 0 |
| 5a | 95 | 48 of 74 | 0 |
| 5b | 28 | 48 of 74 | 0 |
| 6a | 29 | 51 of 74 | 0 |
| 6b | 1 | 51 of 74 | 0 |
The best zone in Montana is 6a, which is not its mildest — 6b is. The count peaks in the middle and falls both ways, because the warm end loses plants to insufficient winter chill and summer heat rather than to cold. Most temperate fruit needs a documented number of hours below about 45 °F to break dormancy and set a crop, so an apple fails in a winter that is too warm; currants and rhubarb cook in the heat that comes with it. See the full list with reasons.
Your own ZIP
Work out your own dates
Each of these takes a ZIP code and answers for that ZIP alone, citing the station it used and how far away it is. There is a ZIP box in the header of every page.
- What survives my winter?
Runs on the hardiness zone, so it answers exactly for your ZIP code rather than for Montana as a whole — 74 perennial fruits, berries, vegetables and herbs.
- When do I start my seeds?
Dates every spring job from your own last freeze — sow indoors, set out, direct sow.
- When do I sow the next round?
How often each crop is worth re-sowing, and when the next sowing is due.
- What can I still plant?
Counts the growing days left before your first fall freeze, crop by crop.
Metro areas in Montana
5 metro areas here have its own page, with the freeze dates from every station serving it, a spring calendar built from those stations, and every ZIP code in it listed with that ZIP code's exact zone and nearest station.
- Billings, MT Zones 4b–5a
- Missoula, MT Zones 5a–6a
- Helena, MT Zones 4b–5a
- Great Falls, MT Zones 4a–4b
- Bozeman, MT Zones 4b–5a
Counties in Montana
24 countys here have its own page, listing every ZIP code in it with that ZIP code's exact zone and nearest station. These are the smaller places outside the metro areas above — where most of Montana's ZIP codes actually are.
- Flathead County, MT Zones 4b–6a
- Lake County, MT Zones 5b–6a
- Madison County, MT Zones 4b–5a
- Big Horn County, MT Zones 4b–5a
- Sheridan County, MT Zones 3b–4a
- Valley County, MT Zones 3b–4a
- Fergus County, MT Zone 4b
- Park County, MT Zones 4a–5a
- Ravalli County, MT Zones 5a–5b
- Rosebud County, MT Zones 4a–5a
- Sanders County, MT Zones 6a–6b
- Beaverhead County, MT Zones 4b–5a
- Blaine County, MT Zones 3b–4b
- Chouteau County, MT Zones 4a–4b
- Hill County, MT Zones 3b–4a
- Lincoln County, MT Zones 5a–6a
- Powder River County, MT Zones 4b–5a
- Garfield County, MT Zones 4a–4b
- Judith Basin County, MT Zone 4b
- Phillips County, MT Zones 3b–4b
- Roosevelt County, MT Zone 4a
- Teton County, MT Zones 4a–4b
- Liberty County, MT Zone 4a
- Pondera County, MT Zones 4a–4b
Other states to compare
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 3b 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 3b, 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
The hardiness zone is the USDA 2023 Plant Hardiness Zone Map, published per ZIP code by PRISM at Oregon State. The freeze dates, growing seasons and summer highs are NOAA's 1991–2020 Climate Normals, read from every station in Montana. Which ZIP codes are in Montana comes from the Census ZIP-to-county relation, since a county's federal code begins with its state's. Nothing here is estimated.
This page names no single station for Montana on purpose. Picking one to represent a state sounds reasonable and is not — the same reason the metro pages refuse it, only more so at this size. Instead every range names the station at each end, so you can check both without either one being made to speak for the state.