Spearfish, SD planting zone & frost dates
Spearfish is in USDA hardiness zone 5b. The last spring frost usually comes around May 12 and the first fall frost around October 2, for a growing season of about 143 days.
Planting calendar for Spearfish
Dates are counted from the average last spring frost (May 12) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Mar 17 – Mar 31 Transplant outdoors: May 19 – May 26 |
| Peppers | Start seeds indoors: Mar 3 – Mar 17 Transplant outdoors: May 26 – Jun 2 |
| Eggplant | Start seeds indoors: Mar 3 – Mar 17 Transplant outdoors: May 26 – Jun 2 |
| Broccoli | Start seeds indoors: Mar 3 – Mar 17 Transplant outdoors: Apr 14 – Apr 28 |
| Cabbage | Start seeds indoors: Mar 3 – Mar 17 Transplant outdoors: Apr 14 – Apr 28 |
| Onions (sets) | Plant outdoors: Apr 14 – Apr 28 |
| Peas | Sow outdoors: Mar 31 – Apr 14 |
| Spinach | Sow outdoors: Mar 31 – Apr 14 |
| Lettuce | Sow outdoors: Apr 14 – Apr 28 |
| Carrots | Sow outdoors: Apr 14 – Apr 28 |
| Potatoes | Plant outdoors: Apr 14 – Apr 28 |
| Beans | Sow outdoors: May 19 – May 26 |
| Sweet corn | Sow outdoors: May 19 – May 26 |
| Cucumbers | Sow outdoors: May 19 – May 26 |
| Squash & zucchini | Sow outdoors: May 19 – May 26 |
| Basil | Start seeds indoors: Mar 31 – Apr 14 Transplant outdoors: May 19 – May 26 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 7 (8 weeks before the average first fall frost on Oct 2).
Useful for zone 5b gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 29 | May 12 | May 25 |
| First 32°F frost in fall is before | Oct 17 | Oct 2 | Sep 21 |
How to read it: in spring there is a 10% chance of a frost after May 25, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 21. A hard freeze (28°F) usually ends around April 30.
Hardiness zone by ZIP code in Spearfish
- 57783 zone 5b
Nearby cities
- Rapid City zone 5b, last frost May 3
- Aberdeen zone 4a, last frost May 8
- Huron zone 4b, last frost May 6
- Mitchell zone 5a, last frost May 2
- Yankton zone 5a, last frost Apr 27
- Watertown zone 4b, last frost May 7
- Brookings zone 4b, last frost May 6
- Vermillion zone 5a, last frost May 3
Questions
What growing zone is Spearfish, SD?
Spearfish is in USDA Plant Hardiness Zone 5b (average extreme winter low -15°F to -10°F), according to the USDA 2023 map.
When is the last frost in Spearfish?
The average last spring frost (32°F) in Spearfish is May 12. There is still a 10% chance of frost until May 25.
When can I plant tomatoes in Spearfish?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 19 – May 26. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Spearfish, SD (USC00397882), 1.2 km (0.7 mi) from the city center, elevation 1107 m, based on 28 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.