USDA zone 4b in South Dakota
USDA plant hardiness zone 4b covers 70 locations across South Dakota (average annual extreme minimum −25 to −20 °F): Akaska, SD, Alpena, SD, Andover, SD, Arlington, SD, Artesian, SD, Belle Fourche, SD, and 64 more. Average last spring frost across this group ranges May 1 (Dell Rapids) to June 1 (Hill), and growing seasons run 102–164 days (Hill to Waubay) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every South Dakota location's own frost dates; the printable planting calendar uses Watertown, this group's median-season location.
- USDA zone
- 4b−25 to −20 °F
- Last frost range
- May 1–Jun 1avg, 32°F
- First frost range
- Sep 10–Oct 12avg, 32°F
- Growing season range
- 102–164days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Akaska | Glenham | Mobridge Muni Ap | May 5 | Oct 4 | 150 |
| Alpena | Virgil | Wessington Springs | May 2 | Oct 8 | 157 |
| Andover | Pierpont | Andover #2 | May 6 | Oct 4 | 150 |
| Arlington | Badger, Lake Norden | Arlington 1 W | May 3 | Oct 2 | 151 |
| Artesian | — | Forestburg 4 Nne | May 9 | Sep 28 | 140 |
| Belle Fourche | — | Belle Fourche 22 Nnw | May 15 | Sep 24 | 130 |
| Big Stone | — | Milbank 4 Nw | May 2 | Oct 4 | 153 |
| Bison | Isabel | Glad Valley 2 W | May 11 | Sep 30 | 140 |
| Bridger | — | Plainview 6 Ssw | May 15 | Sep 27 | 134 |
| Brookings | Volga, White, Aurora, Bruce, Sinai | Brookings 2 Ne | May 6 | Oct 1 | 145 |
| Buffalo | — | Buffalo Asos | May 10 | Oct 1 | 141 |
| Bullhead | McIntosh | Mc Intosh 6 Se | May 9 | Sep 30 | 143 |
| Camp Crook | — | Camp Crook | May 17 | Sep 24 | 128 |
| Carthage | De Smet, Lake Preston, Iroquois, Bryant, Erwin, Oldham | De Smet | May 5 | Oct 4 | 151 |
| Cherry Creek | — | Kirley 6 N | May 6 | Oct 4 | 148 |
| Cherry Creek | — | Milesville 5 Ne | May 8 | Oct 2 | 147 |
| Clark | Shamrock Colony, Doland, Garden, Willow Lake, Raymond, Bradley, +1 more | Clark | May 5 | Oct 5 | 153 |
| Clear Lake | Brandt, Gary, Goodwin, Toronto, Poinsett Colony, La Bolt, +2 more | Clear Lake | May 7 | Oct 1 | 146 |
| Colman | Flandreau, Elkton, Egan, Trent | Flandreau | May 5 | Oct 1 | 148 |
| Dell Rapids | — | Sioux Falls 14 Nne | May 1 | Oct 4 | 155 |
| Eagle Butte | — | Dupree 15 Sse | May 6 | Oct 2 | 148 |
| Edgemont | — | Edgemont | May 23 | Sep 20 | 117 |
| Eureka | — | Eureka | May 12 | Sep 27 | 137 |
| Faith | — | Faith Muni Ap | May 7 | Oct 3 | 147 |
| Faith | — | Maurine 12sw | May 13 | Sep 28 | 136 |
| Faulkton | Rockham, Seneca, Cresbard, Orient | Faulkton 1 Nw | May 10 | Sep 28 | 139 |
| Fort Pierre | — | Ft Pierre 17 Wsw | May 10 | Sep 27 | 138 |
| Fort Thompson | Lower Brule, Stephan | Stephan 2 Nw | May 10 | Sep 29 | 140 |
| Frederick | — | Columbia 8 N | May 7 | Sep 29 | 145 |
| Gann Valley | — | Gann Valley 4nw | May 6 | Oct 1 | 148 |
| Harrold | — | Harrold 12 Ssw | May 17 | Sep 24 | 129 |
| Herreid | — | Pollock | May 8 | Sep 30 | 143 |
| Highmore | Harrold, Ree Heights | Highmore 1 W | May 12 | Oct 1 | 142 |
| Hill | — | Hill City | Jun 1 | Sep 10 | 102 |
| Hosmer | Bowdle, Roscoe, Onaka | Roscoe | May 7 | Oct 3 | 148 |
| Ipswich | — | Ipswich | May 8 | Sep 29 | 143 |
| La Plant | Whitehorse, Little Eagle, Timber Lake | Timber Lake | May 10 | Sep 30 | 141 |
| Lantry | Dupree | Dupree | May 8 | Oct 1 | 144 |
| Lebanon | Swift Bird, Hoven, Tolstoy | Gettysburg | May 7 | Oct 2 | 147 |
| Lemmon | Morristown | Lemmon | May 10 | Sep 30 | 142 |
| Leola | Wetonka | Leola | May 9 | Sep 28 | 141 |
| Madison | Nunda, Chester, Colton, Ramona, Wentworth | Madison 2se | May 5 | Sep 30 | 148 |
| Mansfield | Ashton | Mellette 4 W | May 11 | Sep 27 | 137 |
| McLaughlin | Selfridge | Mc Laughlin | May 12 | Sep 28 | 137 |
| Midland | — | Midland | May 12 | Sep 28 | 138 |
| Milbank | — | Milbank | May 5 | Oct 2 | 150 |
| Morristown | — | Pretty Rock | May 20 | Sep 23 | 124 |
| Oahe Acres | — | Pierre Rgnl Ap | May 6 | Oct 3 | 148 |
| Onida | Blunt, Agar | Onida 4 Nw | May 8 | Oct 2 | 147 |
| Ortley | South Shore, Marvin, Stockholm, Twin Brooks | Summit 1 W | May 14 | Sep 28 | 136 |
| Prairie | Bison | Bison | May 10 | Oct 1 | 144 |
| Prairie | Buffalo | Redig 11 Ne | May 15 | Sep 24 | 131 |
| Redfield | Frankfort | Redfield | May 8 | Oct 1 | 145 |
| Selby | Akaska, Java, Mound | Selby | May 8 | Oct 1 | 145 |
| Sioux Falls | Humboldt | Sioux Falls | May 1 | Oct 6 | 157 |
| Sisseton | Claire, Peever | Sisseton | May 4 | Oct 3 | 151 |
| Turton | — | Turton | May 7 | Oct 3 | 149 |
| Vale | Newell, Nisland | Newell | May 8 | Oct 1 | 144 |
| Vale | Bridger | Red Owl | May 16 | Sep 26 | 131 |
| Veblen | Eden | Roy Lake | May 2 | Oct 9 | 160 |
| Vilas | — | Howard | May 5 | Oct 2 | 149 |
| Wakpala | — | Mobridge 2nnw | May 3 | Oct 8 | 157 |
| Wasta | — | Elm Springs 3 Ese | May 8 | Oct 3 | 146 |
| Watertown * | Henry, Kranzburg, Florence, Hayti, Hazel | Watertown Rgnl Ap | May 7 | Sep 30 | 145 |
| Waubay | Grenville, Roslyn | Waubay Natl Wild Life | May 1 | Oct 12 | 164 |
| Webster | Bristol, Wallace | Webster | May 4 | Oct 6 | 156 |
| Wessington | St. Lawrence, Millerdale Colony, Tulare | Miller | May 3 | Oct 3 | 152 |
| Wilmot | Corona | Wilmot | May 5 | Oct 1 | 149 |
| Winfred | — | Winfred 2s | May 6 | Oct 3 | 151 |
| Wolsey | Morningside, Cavour, Hitchcock, Yale | Huron Rgnl Ap | May 6 | Oct 2 | 146 |
* Watertown is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Watertown, representative)
Computed from Watertown's average frost dates — the median-season location in this South Dakotazone 4b group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Mar 12 – Mar 26 | May 14 – May 21 | Jul 13 – Aug 2 | — | matures comfortably |
| Pepper | Very tender | Feb 26 – Mar 12 | May 21 – May 28 | Jul 20 – Aug 19 | — | matures comfortably |
| Cucumber | Tender | Apr 9 – Apr 16 | May 14 – May 21 | Jul 3 – Jul 23 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 14 – May 21 | Jun 28 – Jul 13 | — | matures comfortably |
| Bush bean | Tender | — | May 14 – May 21 | Jul 3 – Jul 13 | Aug 1 – Aug 11 | matures comfortably |
| Sweet corn | Tender | — | May 7 – May 21 | Jul 6 – Aug 5 | — | matures comfortably |
| Basil | Very tender | Mar 26 – Apr 9 | May 14 – May 21 | Jun 13 – Jun 28 | — | matures comfortably |
| Lettuce | Half-hardy | Mar 26 – Apr 9 | Apr 9 – Apr 23 | May 24 – Jun 8 | Jul 18 – Aug 2 | matures comfortably |
| Pea | Hardy | — | Mar 26 – Apr 9 | May 20 – Jun 4 | Jul 8 – Jul 23 | matures comfortably |
| Spinach | Hardy | — | Mar 26 – Apr 9 | May 5 – May 15 | Jul 28 – Aug 7 | matures comfortably |
| Carrot | Half-hardy | — | Apr 16 – Apr 23 | Jun 15 – Jul 5 | Jun 28 – Jul 18 | matures comfortably |
| Broccoli | Half-hardy | Mar 12 – Mar 26 | Apr 9 – Apr 23 | Jun 3 – Jun 23 | Jul 3 – Jul 23 | matures comfortably |
Which crops fit this growing season
Using Watertown's own 145-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Watertown)
From NOAA's 1991–2020 Climate Normals at station USW00014946. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | May 17 | May 31 | Sep 23 | Oct 4 | 127 |
| 32°F (freeze) | May 7 | May 20 | Sep 30 | Oct 13 | 145 |
| 28°F | Apr 29 | May 11 | Oct 9 | Oct 22 | 164 |
| 24°F | Apr 20 | May 3 | Oct 20 | Nov 2 | 183 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 70 locations is 2,537; Watertown's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 2,370 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,197 | cool-season crops (brassicas, greens) |
Hardiness zone 4b in South Dakota
Zone 4b means an average annual extreme minimum winter temperature of about −25 to −20 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. South Dakota spans 4 hardiness zones in this dataset — see all South Dakota locations for the full range, including zones4a, 5a, 5b.
Explore zone 4b in other states at zone 4b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 4b mean in South Dakota?
- Zone 4b means an average annual extreme minimum winter temperature of −25 to −20 °F — the standard USDA measure of which perennials survive winter. 70 locations in South Dakota fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in South Dakota's zone 4b is the growing season longest?
- Waubay runs the longest season on this page at about 164 days; Hill is shortest at about 102 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in South Dakota's zone 4b?
- Using Watertown's frost dates (this page's median-season location): start seeds indoors about Mar 12 – Mar 26, then transplant outside about May 14 – May 21. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in South Dakota's zone 4b have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 70 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.