USDA Hardiness Zone 5b
Frost Dates for 57701 — Rapid City, South Dakota
NOAA 1991–2020 normals from Rapid City WFO, SD (3,379 ft), under a mile south.
Updated
In Rapid City, the last spring frost (32°F) is around May 3 in half of years and has passed by May 17 in nine years out of ten. The first fall frost comes around October 8, as early as September 26 one year in ten, leaving a typical freeze-free season of 157 days (NOAA, Rapid City WFO, SD).
- Last spring frost
- May 3
- First fall frost
- October 8
- Growing season
- 157 days
- Hardiness zone
- 5b
50% probability
50% probability
freeze-free, 50%
-15 to -10°F (-26.1 to -23.3°C) coldest night
- First snow
- October 19
- Last snow
- April 25
- Winters with snow
- 100%
- Snow per year
- 53.7"
median, 1991–2020
median, 1991–2020
24 of 24 observed
NOAA normal
Frost risk by date in Rapid City
Half of springs at Rapid City WFO, SD see their last 32°F night by May 3; only one in ten is past it by April 20, and one in ten still has one after May 17. Planting tender crops after May 9 leaves a 30% risk of a frost on them, after May 13 20%, and after May 17 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 59% of the 49 South Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 8 in half of years, as early as September 26 one year in ten, and holds off past October 23 one year in ten. A hard freeze of 28°F follows 10 days later, around October 18; in spring the one-in-ten date for 28°F is May 5, 12 days before the 32°F one. The freeze-free season lasts 157 days in a typical year, longer than at 78% of the 49 South Dakota stations; it reaches 176 days one year in ten and falls short of 137 one year in ten. On average 144 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 12 days longer, to about May 15, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 11 and March 25.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 1 | May 5 | May 9 | May 11 | May 15 | May 18 | May 21 | May 24 | May 29 |
| 32°F | Apr 20 | Apr 25 | Apr 29 | May 1 | May 3 | May 6 | May 9 | May 13 | May 17 |
| 28°F | Apr 8 | Apr 13 | Apr 16 | Apr 19 | Apr 22 | Apr 25 | Apr 28 | May 1 | May 5 |
| 24°F | Mar 27 | Apr 2 | Apr 6 | Apr 9 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 25 |
| 20°F | Mar 14 | Mar 22 | Mar 28 | Mar 31 | Apr 2 | Apr 6 | Apr 9 | Apr 13 | Apr 18 |
| 16°F | Mar 3 | Mar 10 | Mar 15 | Mar 21 | Mar 25 | Mar 30 | Apr 1 | Apr 5 | Apr 12 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 19 | Sep 23 | Sep 26 | Sep 28 | Oct 1 | Oct 2 | Oct 5 | Oct 8 | Oct 14 |
| 32°F | Sep 26 | Sep 29 | Oct 1 | Oct 5 | Oct 8 | Oct 11 | Oct 15 | Oct 18 | Oct 23 |
| 28°F | Oct 3 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 24 | Oct 27 | Nov 1 |
| 24°F | Oct 12 | Oct 17 | Oct 20 | Oct 23 | Oct 27 | Oct 29 | Nov 1 | Nov 5 | Nov 11 |
| 20°F | Oct 19 | Oct 25 | Oct 28 | Nov 1 | Nov 3 | Nov 7 | Nov 10 | Nov 14 | Nov 19 |
| 16°F | Oct 27 | Oct 31 | Nov 3 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 22 | Nov 28 |
Freeze probabilities 1991–2020 at Rapid City WFO, SD, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 57701 →Compare Rapid City with another place →
Weather by month in Rapid City
July is the warmest month at Rapid City WFO, SD, averaging 84°F by day and 62°F at night; January is the coldest at 37°F and 16°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 62% of years.
Warmth for growing adds up to 2,664 growing degree days a year (base 50°F), fewer than at 55% of the 49 South Dakota stations. 28% of them (755) have built up by the end of June, and July adds the most, 713. Precipitation totals 20.0 inches a year, most in May (4.1") and least in January (0.3"); May to September bring 68% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 37 | 16 | 0.3 | 100% | 27 | 2 |
| Feb | 38 | 18 | 0.5 | 100% | 25 | 5 |
| Mar | 47 | 26 | 0.9 | 100% | 23 | 22 |
| Apr | 55 | 34 | 2.3 | 100% | 12 | 55 |
| May | 65 | 45 | 4.1 | 62% | 2 | 207 |
| Jun | 76 | 55 | 3.3 | 1% | <1 | 465 |
| Jul | 84 | 62 | 2.6 | 0% | 0 | 713 |
| Aug | 83 | 60 | 2.2 | 0% | 0 | 671 |
| Sep | 74 | 51 | 1.4 | 24% | <1 | 389 |
| Oct | 59 | 38 | 1.5 | 98% | 8 | 111 |
| Nov | 47 | 27 | 0.5 | 100% | 20 | 23 |
| Dec | 38 | 19 | 0.4 | 100% | 27 | 2 |
Monthly normals 1991–2020 at Rapid City WFO, SD (3,379 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Rapid City 4NW, SD, 4 miles northwest of Rapid City, has a last frost 7 days later (May 10), a first frost 3 days earlier (October 5), a season 10 days shorter.
When it snows in Rapid City, South Dakota
The first measurable snow (0.1 inch or more) in Rapid City usually arrives around October 19, and the last of the season around April 25. Those are the middle dates across the winters of 1991–2020 at Rapid City WFO, SD, 0.9 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 8 days after the last snow.
Planting calendar for 57701
| When | What to do |
|---|---|
| February 22 – March 8 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 8 – March 22 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 5 – April 19 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 3 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 16 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 24 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 8 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 57701 is under a mile from Rapid City WFO, SD, which stands at 3,379 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 57701 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across South Dakota →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.