USDA Hardiness Zone 4b
Frost Dates for 57601 — Mobridge, South Dakota
NOAA 1991–2020 normals from Mobridge Municipal Airport, SD (1,715 ft), 6 miles northeast.
Updated
In Mobridge, the last spring frost (32°F) is around May 5 in half of years and has passed by May 20 in nine years out of ten. The first fall frost comes around October 4, as early as September 21 one year in ten, leaving a typical freeze-free season of 150 days (NOAA, Mobridge Municipal Airport, SD).
- Last spring frost
- May 5
- First fall frost
- October 4
- Growing season
- 150 days
- Hardiness zone
- 4b
50% probability
50% probability
freeze-free, 50%
-25 to -20°F (-31.7 to -28.9°C) coldest night
- First snow
- November 7
- Last snow
- April 4
- Winters with snow
- 100%
- Snow per year
- 31"
median, 1991–2020
median, 1991–2020
16 of 16 observed
NOAA normal
Frost risk by date in Mobridge
Half of springs at Mobridge Municipal Airport, SD see their last 32°F night by May 5; only one in ten is past it by April 23, and one in ten still has one after May 20. Planting tender crops after May 11 leaves a 30% risk of a frost on them, after May 15 20%, and after May 20 10%. The 15 days between the even-odds date and the one-in-ten date is wider than at 84% of the 49 South Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 4 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 8 days later, around October 12; in spring the one-in-ten date for 28°F is May 10, 10 days before the 32°F one. The freeze-free season lasts 150 days in a typical year, longer than at 53% of the 49 South Dakota stations; it reaches 169 days one year in ten and falls short of 132 one year in ten. On average 171 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 11 days longer, to about May 16, and return around September 26. Severe cold of 16°F or below comes every winter, usually between November 9 and April 1.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 4 | May 8 | May 11 | May 14 | May 16 | May 19 | May 22 | May 25 | May 30 |
| 32°F | Apr 23 | Apr 28 | May 1 | May 3 | May 5 | May 8 | May 11 | May 15 | May 20 |
| 28°F | Apr 13 | Apr 18 | Apr 21 | Apr 25 | Apr 28 | Apr 30 | May 3 | May 5 | May 10 |
| 24°F | Apr 3 | Apr 8 | Apr 11 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 28 | May 2 |
| 20°F | Mar 25 | Mar 31 | Apr 3 | Apr 6 | Apr 9 | Apr 12 | Apr 15 | Apr 19 | Apr 24 |
| 16°F | Mar 12 | Mar 19 | Mar 24 | Mar 30 | Apr 1 | Apr 4 | Apr 7 | Apr 10 | Apr 17 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 13 | Sep 18 | Sep 22 | Sep 24 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 8 |
| 32°F | Sep 21 | Sep 26 | Sep 30 | Oct 2 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 17 |
| 28°F | Sep 29 | Oct 3 | Oct 7 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 26 |
| 24°F | Oct 7 | Oct 12 | Oct 17 | Oct 20 | Oct 22 | Oct 25 | Oct 28 | Nov 1 | Nov 5 |
| 20°F | Oct 18 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 10 | Nov 14 |
| 16°F | Oct 27 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 14 | Nov 17 | Nov 22 |
Freeze probabilities 1991–2020 at Mobridge Municipal Airport, 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 57601 →Compare Mobridge with another place →
Weather by month in Mobridge
July is the warmest month at Mobridge Municipal Airport, SD, averaging 87°F by day and 62°F at night; January is the coldest at 27°F and 6°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 72% of years.
Warmth for growing adds up to 2,857 growing degree days a year (base 50°F), more than at 67% of the 49 South Dakota stations. 31% of them (877) have built up by the end of June, and July adds the most, 759. Precipitation totals 18.0 inches a year, most in June (3.1") and least in January (0.4"); May to September bring 66% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 27 | 6 | 0.4 | 100% | 31 | 0 |
| Feb | 32 | 11 | 0.7 | 100% | 27 | 0 |
| Mar | 45 | 22 | 0.7 | 100% | 27 | 12 |
| Apr | 59 | 33 | 1.6 | 100% | 15 | 64 |
| May | 70 | 45 | 2.9 | 72% | 3 | 264 |
| Jun | 80 | 56 | 3.1 | 0% | 0 | 538 |
| Jul | 87 | 62 | 2.3 | 0% | 0 | 759 |
| Aug | 86 | 60 | 2.1 | 0% | 0 | 707 |
| Sep | 77 | 50 | 1.5 | 33% | 1 | 404 |
| Oct | 60 | 37 | 1.8 | 100% | 11 | 104 |
| Nov | 44 | 23 | 0.4 | 100% | 26 | 6 |
| Dec | 32 | 12 | 0.5 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Mobridge Municipal Airport, SD (1,715 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, Mc Laughlin, SD, 29 miles northwest of Mobridge and 286 feet higher, has a last frost 7 days later (May 12), a first frost 6 days earlier (September 28), a season 13 days shorter.
When it snows in Mobridge, South Dakota
The first measurable snow (0.1 inch or more) in Mobridge usually arrives around November 7, and the last of the season around April 4. Those are the middle dates across the winters of 1991–2020 at Mobridge Municipal Airport, SD, 5.7 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 31 days after the last snow.
Planting calendar for 57601
| When | What to do |
|---|---|
| February 24 – March 10 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 10 – March 24 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 7 – April 21 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 5 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 12 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 20 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 4 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 57601 is 6 miles from Mobridge Municipal Airport, SD, which stands at 1,715 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 57601 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°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.