USDA Hardiness Zone 5b
Frost Dates for 57783 — Spearfish, South Dakota
NOAA 1991–2020 normals from Spearfish, SD (3,633 ft), under a mile northeast.
Updated
In Spearfish, the last spring frost (32°F) is around May 12 in half of years and has passed by May 25 in nine years out of ten. The first fall frost comes around October 2, as early as September 21 one year in ten, leaving a typical freeze-free season of 143 days (NOAA, Spearfish, SD).
- Last spring frost
- May 12
- First fall frost
- October 2
- Growing season
- 143 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 25
- Last snow
- April 25
- Winters with snow
- 91%
- Snow per year
- 70.5"
median, 1991–2020
median, 1991–2020
20 of 22 observed
NOAA normal
Frost risk by date in Spearfish
Half of springs at Spearfish, SD see their last 32°F night by May 12; only one in ten is past it by April 29, and one in ten still has one after May 25. Planting tender crops after May 17 leaves a 30% risk of a frost on them, after May 20 20%, and after May 25 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 43% of the 49 South Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 2 in half of years, as early as September 21 one year in ten, and holds off past October 17 one year in ten. A hard freeze of 28°F follows 10 days later, around October 12; in spring the one-in-ten date for 28°F is May 14, 11 days before the 32°F one. The freeze-free season lasts 143 days in a typical year, shorter than at 76% of the 49 South Dakota stations; it reaches 162 days one year in ten and falls short of 123 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 10 days longer, to about May 22, and return around September 25. Severe cold of 16°F or below comes every winter, usually between November 5 and March 31.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 11 | May 15 | May 18 | May 20 | May 22 | May 25 | May 28 | May 31 | Jun 4 |
| 32°F | Apr 29 | May 3 | May 6 | May 9 | May 12 | May 15 | May 17 | May 20 | May 25 |
| 28°F | Apr 16 | Apr 20 | Apr 24 | Apr 27 | Apr 30 | May 2 | May 5 | May 9 | May 14 |
| 24°F | Apr 3 | Apr 7 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 27 | Apr 30 |
| 20°F | Mar 20 | Mar 29 | Apr 2 | Apr 5 | Apr 8 | Apr 11 | Apr 14 | Apr 18 | Apr 22 |
| 16°F | Mar 9 | Mar 17 | Mar 23 | Mar 29 | Mar 31 | Apr 3 | Apr 6 | Apr 11 | Apr 16 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 9 | Sep 15 | Sep 19 | Sep 22 | Sep 25 | Sep 27 | Sep 30 | Oct 1 | Oct 6 |
| 32°F | Sep 21 | Sep 26 | Sep 29 | Oct 1 | Oct 2 | Oct 5 | Oct 9 | Oct 13 | Oct 17 |
| 28°F | Sep 29 | Oct 2 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 25 |
| 24°F | Oct 5 | Oct 10 | Oct 14 | Oct 17 | Oct 20 | Oct 24 | Oct 27 | Oct 31 | Nov 4 |
| 20°F | Oct 12 | Oct 17 | Oct 22 | Oct 25 | Oct 29 | Nov 1 | Nov 5 | Nov 9 | Nov 16 |
| 16°F | Oct 20 | Oct 26 | Oct 30 | Nov 2 | Nov 5 | Nov 9 | Nov 13 | Nov 19 | Nov 24 |
Freeze probabilities 1991–2020 at Spearfish, 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 57783 →Compare Spearfish with another place →
Weather by month in Spearfish
July is the warmest month at Spearfish, SD, averaging 84°F by day and 58°F at night; January is the coldest at 36°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 85% of years.
Warmth for growing adds up to 2,333 growing degree days a year (base 50°F), fewer than at 90% of the 49 South Dakota stations. 27% of them (637) have built up by the end of June, and July adds the most, 638. Precipitation totals 21.4 inches a year, most in May (3.7") and least in January (0.6"); May to September bring 61% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 36 | 16 | 0.6 | 100% | 26 | 2 |
| Feb | 37 | 16 | 0.9 | 100% | 24 | 3 |
| Mar | 46 | 24 | 1.2 | 100% | 22 | 16 |
| Apr | 55 | 32 | 2.2 | 100% | 13 | 46 |
| May | 64 | 42 | 3.7 | 85% | 2 | 168 |
| Jun | 75 | 51 | 3.5 | 2% | 0 | 404 |
| Jul | 84 | 58 | 2.4 | 0% | 0 | 638 |
| Aug | 83 | 56 | 1.9 | 0% | 0 | 605 |
| Sep | 74 | 48 | 1.6 | 38% | 1 | 344 |
| Oct | 58 | 35 | 2.0 | 100% | 9 | 92 |
| Nov | 46 | 26 | 0.7 | 100% | 20 | 16 |
| Dec | 37 | 18 | 0.7 | 100% | 27 | 1 |
Monthly normals 1991–2020 at Spearfish, SD (3,633 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, Deadwood, SD, 11 miles southeast of Spearfish and 1,037 feet higher, has a last frost 12 days later (May 24), a first frost 7 days earlier (September 25), a season 18 days shorter.
When it snows in Spearfish, South Dakota
The first measurable snow (0.1 inch or more) in Spearfish usually arrives around October 25, and the last of the season around April 25. Those are the middle dates across the winters of 1991–2020 at Spearfish, SD, 0.7 miles away: half of years saw snow earlier, half later. Snow fell in 91% of those winters. The last 32°F night of spring typically comes 17 days after the last snow.
Planting calendar for 57783
| When | What to do |
|---|---|
| March 3 – March 17 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 17 – March 31 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 14 – April 28 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 12 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 10 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 18 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 2 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 57783 is under a mile from Spearfish, SD, which stands at 3,633 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 57783 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.