In Rapid City, SD, the average last spring frost is May 12 and the average first fall frost is Oct 1, which leaves about 139 frost-free days for the garden. These dates come from NOAA climate normals for the Rapid City Rgnl Airport, SD weather station, at 3,160 feet above sea level.
A moderate season leaves room for most vegetables. Start warm-season crops indoors for a head start, plant cool-season crops early and again in late summer, and keep row cover ready for surprise frosts. Frost timing varies from year to year: in about 1 spring in 10 the last frost falls as late as May 26, and in about 1 fall in 10 the first frost arrives as early as Sep 16.
Frost dates for Rapid City, SD
| Chance of a freeze (32°F) after or before this date | Last spring frost | First fall frost | Freeze-free season |
|---|---|---|---|
| Optimistic (about 1 year in 10) | May 1 | Oct 14 | 166 days |
| Average (half of years) | May 12 | Oct 1 | 139 days |
| Cautious (9 years in 10 are safe) | May 26 | Sep 16 | 113 days |
Source: NOAA NCEI U.S. Climate Normals, 1991 to 2020. Use the cautious dates for tender crops such as tomatoes and peppers.
When to plant in Rapid City, SD
These windows count weeks forward and back from the average frost dates above. They are planning guides: check the forecast before planting tender crops, and see our what to plant now tool for today's date.
| Crop | Start seeds indoors | Plant outdoors in spring | Plant in fall |
|---|---|---|---|
| Tomatoes | Mar 17 to Mar 31 | May 19 to May 26 | – |
| Peppers | Mar 3 to Mar 17 | May 26 to Jun 2 | – |
| Eggplant | Mar 3 to Mar 17 | May 26 to Jun 2 | – |
| Onions | Mar 3 to Mar 17 | Apr 14 to Apr 28 | – |
| Parsley | Mar 3 to Mar 17 | May 12 to May 19 | – |
| Broccoli, cabbage, cauliflower | Mar 17 to Mar 31 | Apr 28 to May 5 | Jul 9 to Aug 6 |
| Basil | Mar 31 to Mar 31 | May 19 to May 26 | – |
| Peas | Sow outdoors | Mar 31 to Apr 14 | Jul 9 to Aug 6 |
| Spinach | Sow outdoors | Mar 31 to Apr 14 | Aug 6 to Sep 3 |
| Radishes | Sow outdoors | Mar 31 to Apr 14 | Aug 6 to Sep 3 |
| Lettuce | Sow outdoors | Apr 14 to Apr 28 | Aug 6 to Sep 3 |
| Carrots | Sow outdoors | Apr 14 to Apr 28 | Jul 9 to Aug 6 |
| Beets | Sow outdoors | Apr 14 to Apr 28 | Jul 9 to Aug 6 |
| Potatoes | Sow outdoors | Apr 14 to Apr 28 | – |
| Kale | Sow outdoors | Apr 14 to Apr 28 | Jul 9 to Aug 6 |
| Swiss chard | Sow outdoors | Apr 28 to May 12 | – |
| Cilantro | Sow outdoors | Apr 28 to May 12 | Aug 6 to Sep 3 |
| Dill | Sow outdoors | May 12 to May 19 | – |
| Bush beans | Sow outdoors | May 19 to May 26 | Jun 28 to Jul 12 |
| Pole beans | Sow outdoors | May 19 to May 26 | – |
| Sweet corn | Sow outdoors | May 19 to May 26 | – |
| Cucumbers | Sow outdoors | May 19 to May 26 | Jun 18 to Jul 2 |
| Zucchini and summer squash | Sow outdoors | May 19 to May 26 | Jun 28 to Jul 12 |
| Winter squash | Sow outdoors | May 19 to May 26 | – |
| Sweet potatoes (slips) | Sow outdoors | May 26 to Jun 9 | – |
| Okra | Sow outdoors | May 26 to Jun 9 | – |
A dash in the fall column means the crop is not usually planted in fall, or the season is too short.
Overnight lows this week
The National Weather Service forecast shows frost risk on: Sun 15 night (33°F), Wed 18 night (26°F), Thu 19 night (31°F), Fri 20 night (27°F), Sat 21 night (21°F). Cover tender plants before dark on those nights.
| Night | Forecast low | Frost risk |
|---|---|---|
| Sun 15 night | 33°F | Frost possible |
| Mon 16 night | 37°F | No frost expected |
| Tue 17 night | 37°F | No frost expected |
| Wed 18 night | 26°F | Freeze |
| Thu 19 night | 31°F | Freeze |
| Fri 20 night | 27°F | Freeze |
| Sat 21 night | 21°F | Freeze |
Live forecast for the station location, from the National Weather Service. For your own ZIP code, use our garden weather forecast.
More garden tools for Rapid City, SD
- Frost dates by ZIP code for your exact location
- What to plant now, based on today's date
- Garden weather forecast by ZIP code
- Safe transplant date calculator
Frequently asked questions
When is the last frost in Rapid City, SD?
The average last spring frost is May 12. A late frost as far out as May 26 happens in about 1 year in 10, so tender plants such as tomatoes and peppers are safest after that cautious date.
When is the first frost in Rapid City, SD?
The average first fall frost is Oct 1. It can arrive as early as Sep 16 in about 1 year in 10, so plan to harvest tender crops before then.
How long is the growing season in Rapid City, SD?
The average freeze-free season is about 139 days, between the average last spring frost and the average first fall frost.
Where do these dates come from?
They come from the NOAA 1991 to 2020 U.S. Climate Normals for the Rapid City Rgnl Airport, SD station. Hills, valleys, lakes and city heat can shift frost by a week or more, so compare with neighbors who garden near you.