What USDA hardiness zone is Fall River County, South Dakota?

Fall River County, South Dakota spans USDA hardiness zones 4b to 5a. 80% of its ZIP codes are zone 5a, so there is no single zone for the county.

When is the last spring frost in Fall River County, South Dakota?

The median last spring freeze runs May 15 – May 23 across the 4 NOAA weather stations serving Fall River County, South Dakota, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

South Dakota

Planting zones in Fall River County, South Dakota

This county spans USDA zones 4b to 5a, so there is no single zone for Fall River County and anyone who gives you one is rounding. 80% of its ZIP codes are zone 5a; the rest are not.

USDA zones 4b–5a 2 zones across 5 ZIP codes

ZIP codes 5 5 have a NOAA station within range

Weather stations 4 NOAA 1991–2020 normals, across 1,740 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Fall River County, South Dakota 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 Fall River County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 20 – September 30 across the 4 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around March 20 – March 28 — counted back from a last spring freeze of May 15 – 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 4 stations agreeAt least one station

Every one of the 4 NOAA stations serving this county counts May 23 – September 20 as growing season (120 days). Widening to any single station gives May 15 – September 30 (138 days).

Which zone you are in depends where you are

Fall River 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 80% in zone 5a and wrong for the other 20%. Here is the actual split.

Zone	ZIP codes	Share
5a	4	80%
4b	1	20%

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 15 – May 23

First fall freeze September 20 – September 30

Across the 4 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 117–137 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 85.4–85.8 °F in June–August. Summer rain over the same months runs 6.3–7.5" across those 4 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 56% 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 86 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Fall River 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
57735	4b	Edgemont, SD	3.9 km
57747	5a	Hot Springs, SD	8.0 km
57763	5a	Oelrichs, SD	7.2 km
57766	5a	Oral, SD	9.0 km
57782	5a	Oelrichs, SD	8.3 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 Fall River County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 4 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	March 20 – March 28	8 wk before
🌶️ Peppers	Start indoors	March 20 – March 28	8 wk before
🥦 Broccoli	Start indoors	April 3 – April 11	6 wk before
🥬 Cabbage	Start indoors	April 3 – April 11	6 wk before
🥬 Collards	Start indoors	April 3 – April 11	6 wk before
🥬 Kale	Start indoors	April 3 – April 11	6 wk before
🥬 Leaf Lettuce	Start indoors	April 3 – April 11	6 wk before
🫛 Peas	Direct sow	April 3 – April 11	6 wk before
🥬 Spinach	Direct sow	April 3 – April 11	6 wk before
🍠 Sweet Potato	Start indoors	April 3 – April 11	6 wk before
🍅 Tomatoes	Start indoors	April 3 – April 11	6 wk before
🥬 Bok Choy	Start indoors	April 10 – April 18	5 wk before
🥬 Kohlrabi	Start indoors	April 10 – April 18	5 wk before
🥬 Swiss Chard	Start indoors	April 10 – April 18	5 wk before
🥬 Arugula	Direct sow	April 17 – April 25	4 wk before
🥬 Baby Salad Greens	Direct sow	April 17 – April 25	4 wk before
🥕 Beets	Direct sow	April 17 – April 25	4 wk before
🧅 Green Onions	Direct sow	April 17 – April 25	4 wk before
🥬 Mustard Greens	Direct sow	April 17 – April 25	4 wk before
🌶️ Okra	Start indoors	April 17 – April 25	4 wk before
🌱 Radishes	Direct sow	April 17 – April 25	4 wk before
🥔 Turnips	Direct sow	April 17 – April 25	4 wk before
🥬 Cabbage	Set out	April 24 – May 2	3 wk before
🥕 Carrots	Direct sow	April 24 – May 2	3 wk before
🥬 Collards	Direct sow	April 24 – May 2	3 wk before
🥬 Collards	Set out	April 24 – May 2	3 wk before
🥒 Cucumbers	Start indoors	April 24 – May 2	3 wk before
🧅 Green Onions	Set out	April 24 – May 2	3 wk before
🥬 Kale	Direct sow	April 24 – May 2	3 wk before
🥬 Kale	Set out	April 24 – May 2	3 wk before
🥬 Kohlrabi	Direct sow	April 24 – May 2	3 wk before
🥬 Kohlrabi	Set out	April 24 – May 2	3 wk before
🥬 Leaf Lettuce	Direct sow	April 24 – May 2	3 wk before
🎃 Pumpkins	Start indoors	April 24 – May 2	3 wk before
🎃 Summer Squash	Start indoors	April 24 – May 2	3 wk before
🎃 Winter Squash	Start indoors	April 24 – May 2	3 wk before
🥒 Zucchini	Start indoors	April 24 – May 2	3 wk before
🥬 Bok Choy	Direct sow	May 1 – May 9	2 wk before
🥬 Bok Choy	Set out	May 1 – May 9	2 wk before
🥦 Broccoli	Set out	May 1 – May 9	2 wk before
🌿 Cilantro	Direct sow	May 1 – May 9	2 wk before
🥬 Leaf Lettuce	Set out	May 1 – May 9	2 wk before
🥬 Swiss Chard	Direct sow	May 1 – May 9	2 wk before
🥬 Swiss Chard	Set out	May 1 – May 9	2 wk before
🌿 Dill	Direct sow	May 8 – May 16	1 wk before
🫘 Bush Beans	Direct sow	May 22 – May 30	1 wk after
🥒 Cucumbers	Set out	May 22 – May 30	1 wk after
🎃 Pumpkins	Direct sow	May 22 – May 30	1 wk after
🎃 Pumpkins	Set out	May 22 – May 30	1 wk after
🎃 Summer Squash	Direct sow	May 22 – May 30	1 wk after
🎃 Summer Squash	Set out	May 22 – May 30	1 wk after
🌽 Sweet Corn	Direct sow	May 22 – May 30	1 wk after
🍅 Tomatoes	Set out	May 22 – May 30	1 wk after
🎃 Winter Squash	Direct sow	May 22 – May 30	1 wk after
🎃 Winter Squash	Set out	May 22 – May 30	1 wk after
🥒 Zucchini	Direct sow	May 22 – May 30	1 wk after
🥒 Zucchini	Set out	May 22 – May 30	1 wk after
🥒 Cucumbers	Direct sow	May 29 – June 6	2 wk after
🌶️ Okra	Direct sow	May 29 – June 6	2 wk after
🌶️ Okra	Set out	May 29 – June 6	2 wk after
🌶️ Peppers	Set out	May 29 – June 6	2 wk after
🫘 Southern Peas	Direct sow	May 29 – June 6	2 wk after
🍠 Sweet Potato	Set out	May 29 – 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 Fall River County

Zone 5a carries 48 of 74 perennial edibles; zone 4b 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 15 – May 23 across 4 stations; May 4 is the optimistic end.
First fall freeze: Plan to September 6 to be careful. Median September 20 – September 30 across 4 stations; October 13 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 4 stations behind these numbers

All 4 NOAA stations whose normals this page quotes, spanning about 28 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
Edgemont, SD	USC00392557	May 23	September 20	117 days
Hot Springs, SD	USC00394007	May 16	September 27	133 days
Oelrichs, SD	USC00396212	May 15	September 30	137 days
Oral, SD	USC00396304	May 15	September 27	133 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

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

More of South Dakota

Counties with the same zones — 4b–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 4b 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 4b, 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.