Montana
Planting zones in Sheridan County, Montana
This county spans USDA zones 3b to 4a, so there is no single zone for Sheridan County and anyone who gives you one is rounding. 90% of its ZIP codes are zone 3b; the rest are not.
Your ZIP code
Get the exact answer for your address
Everything above describes Sheridan 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 Sheridan County is closing
Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 7 – September 23 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 21 – April 2 — counted back from a last spring freeze of May 16 – May 28 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 28 – September 7 as growing season (102 days). Widening to any single station gives May 16 – September 23 (130 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.
Which zone you are in depends where you are
Sheridan 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 90% in zone 3b and wrong for the other 10%. Here is the actual split.
| Zone | ZIP codes | Share | |
|---|---|---|---|
| 3b | 9 | 90% | |
| 4a | 1 | 10% |
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 101–125 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 77.7–80.1 °F in June–August. Summer rain over the same months runs 7.0–7.7" 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 54% 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 80 °F summer afternoon drying the soil faster than a cool one.
Every ZIP code in Sheridan 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 |
|---|---|---|---|
| 59211 | 3b | Plentywood, MT | 18.0 km |
| 59219 | 3b | Medicine Lake 3 SE, MT | 23.8 km |
| 59242 | 3b | Medicine Lake 3 SE, MT | 8.0 km |
| 59247 | 3b | Medicine Lake 3 SE, MT | 6.5 km |
| 59252 | 3b | Redstone, MT | 16.1 km |
| 59254 | 3b | Plentywood, MT | 6.0 km |
| 59256 | 4a | Raymond Border Stn, MT | 10.1 km |
| 59257 | 3b | Redstone, MT | 7.3 km |
| 59258 | 3b | Medicine Lake 3 SE, MT | 18.7 km |
| 59275 | 3b | Westby, MT | 7.8 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 Sheridan 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 21 – April 2 | 8 wk before |
| 🌶️ Peppers | Start indoors | March 21 – April 2 | 8 wk before |
| 🥦 Broccoli | Start indoors | April 4 – April 16 | 6 wk before |
| 🥬 Cabbage | Start indoors | April 4 – April 16 | 6 wk before |
| 🥬 Collards | Start indoors | April 4 – April 16 | 6 wk before |
| 🥬 Kale | Start indoors | April 4 – April 16 | 6 wk before |
| 🥬 Leaf Lettuce | Start indoors | April 4 – April 16 | 6 wk before |
| 🫛 Peas | Direct sow | April 4 – April 16 | 6 wk before |
| 🥬 Spinach | Direct sow | April 4 – April 16 | 6 wk before |
| 🍠 Sweet Potato | Start indoors | April 4 – April 16 | 6 wk before |
| 🍅 Tomatoes | Start indoors | April 4 – April 16 | 6 wk before |
| 🥬 Bok Choy | Start indoors | April 11 – April 23 | 5 wk before |
| 🥬 Kohlrabi | Start indoors | April 11 – April 23 | 5 wk before |
| 🥬 Swiss Chard | Start indoors | April 11 – April 23 | 5 wk before |
| 🥬 Arugula | Direct sow | April 18 – April 30 | 4 wk before |
| 🥬 Baby Salad Greens | Direct sow | April 18 – April 30 | 4 wk before |
| 🥕 Beets | Direct sow | April 18 – April 30 | 4 wk before |
| 🧅 Green Onions | Direct sow | April 18 – April 30 | 4 wk before |
| 🥬 Mustard Greens | Direct sow | April 18 – April 30 | 4 wk before |
| 🌶️ Okra | Start indoors | April 18 – April 30 | 4 wk before |
| 🌱 Radishes | Direct sow | April 18 – April 30 | 4 wk before |
| 🥔 Turnips | Direct sow | April 18 – April 30 | 4 wk before |
| 🥬 Cabbage | Set out | April 25 – May 7 | 3 wk before |
| 🥕 Carrots | Direct sow | April 25 – May 7 | 3 wk before |
| 🥬 Collards | Direct sow | April 25 – May 7 | 3 wk before |
| 🥬 Collards | Set out | April 25 – May 7 | 3 wk before |
| 🥒 Cucumbers | Start indoors | April 25 – May 7 | 3 wk before |
| 🧅 Green Onions | Set out | April 25 – May 7 | 3 wk before |
| 🥬 Kale | Direct sow | April 25 – May 7 | 3 wk before |
| 🥬 Kale | Set out | April 25 – May 7 | 3 wk before |
| 🥬 Kohlrabi | Direct sow | April 25 – May 7 | 3 wk before |
| 🥬 Kohlrabi | Set out | April 25 – May 7 | 3 wk before |
| 🥬 Leaf Lettuce | Direct sow | April 25 – May 7 | 3 wk before |
| 🎃 Pumpkins | Start indoors | April 25 – May 7 | 3 wk before |
| 🎃 Summer Squash | Start indoors | April 25 – May 7 | 3 wk before |
| 🎃 Winter Squash | Start indoors | April 25 – May 7 | 3 wk before |
| 🥒 Zucchini | Start indoors | April 25 – May 7 | 3 wk before |
| 🥬 Bok Choy | Direct sow | May 2 – May 14 | 2 wk before |
| 🥬 Bok Choy | Set out | May 2 – May 14 | 2 wk before |
| 🥦 Broccoli | Set out | May 2 – May 14 | 2 wk before |
| 🌿 Cilantro | Direct sow | May 2 – May 14 | 2 wk before |
| 🥬 Leaf Lettuce | Set out | May 2 – May 14 | 2 wk before |
| 🥬 Swiss Chard | Direct sow | May 2 – May 14 | 2 wk before |
| 🥬 Swiss Chard | Set out | May 2 – May 14 | 2 wk before |
| 🌿 Dill | Direct sow | May 9 – May 21 | 1 wk before |
| 🫘 Bush Beans | Direct sow | May 23 – June 4 | 1 wk after |
| 🥒 Cucumbers | Set out | May 23 – June 4 | 1 wk after |
| 🎃 Pumpkins | Direct sow | May 23 – June 4 | 1 wk after |
| 🎃 Pumpkins | Set out | May 23 – June 4 | 1 wk after |
| 🎃 Summer Squash | Direct sow | May 23 – June 4 | 1 wk after |
| 🎃 Summer Squash | Set out | May 23 – June 4 | 1 wk after |
| 🌽 Sweet Corn | Direct sow | May 23 – June 4 | 1 wk after |
| 🍅 Tomatoes | Set out | May 23 – June 4 | 1 wk after |
| 🎃 Winter Squash | Direct sow | May 23 – June 4 | 1 wk after |
| 🎃 Winter Squash | Set out | May 23 – June 4 | 1 wk after |
| 🥒 Zucchini | Direct sow | May 23 – June 4 | 1 wk after |
| 🥒 Zucchini | Set out | May 23 – June 4 | 1 wk after |
| 🥒 Cucumbers | Direct sow | May 30 – June 11 | 2 wk after |
| 🌶️ Okra | Direct sow | May 30 – June 11 | 2 wk after |
| 🌶️ Okra | Set out | May 30 – June 11 | 2 wk after |
| 🌶️ Peppers | Set out | May 30 – June 11 | 2 wk after |
| 🫘 Southern Peas | Direct sow | May 30 – June 11 | 2 wk after |
| 🍠 Sweet Potato | Set out | May 30 – June 11 | 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 Sheridan County
Zone 4a carries 34 of 74 perennial edibles; zone 3b carries 17. 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 13 to be careful. Median May 16 – May 28 across 5 stations; May 4 is the optimistic end.
- First fall freeze
- Plan to August 22 to be careful. Median September 7 – September 23 across 5 stations; October 3 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 57 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 |
|---|---|---|---|---|
| Medicine Lake 3 SE, MT | USC00245572 | May 16 | September 18 | 125 days |
| Plentywood, MT | USC00246586 | May 25 | September 14 | 111 days |
| Raymond Border Stn, MT | USC00246893 | May 19 | September 23 | 125 days |
| Redstone, MT | USC00246927 | May 28 | September 7 | 101 days |
| Westby, MT | USC00248777 | May 18 | September 21 | 125 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
Sheridan 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
- Valley County, MT 3b–4a
- Fergus County, MT 4b
- Park County, MT 4a–5a
- Ravalli County, MT 5a–5b
- Rosebud County, MT 4a–5a
- Sanders County, MT 6a–6b
- Beaverhead County, MT 4b–5a
- Blaine County, MT 3b–4b
- Chouteau County, MT 4a–4b
- Hill County, MT 3b–4a
- Lincoln County, MT 5a–6a
- Powder River County, MT 4b–5a
Counties with the same zones — 3b–4a
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 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
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.