USDA Hardiness Zone 4b
Frost Dates for 57451 — Ipswich, South Dakota
NOAA 1991–2020 normals from Ipswich, SD (1,547 ft), 1 miles northwest.
Updated
In Ipswich, the last spring frost (32°F) is around May 8 in half of years and has passed by May 22 in nine years out of ten. The first fall frost comes around September 29, as early as September 17 one year in ten, leaving a typical freeze-free season of 143 days (NOAA, Ipswich, SD).
- Last spring frost
- May 8
- First fall frost
- September 29
- Growing season
- 143 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 9
- Last snow
- April 6
- Winters with snow
- 100%
- Snow per year
- 33.7"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Ipswich
Half of springs at Ipswich, SD see their last 32°F night by May 8; only one in ten is past it by April 26, and one in ten still has one after May 22. Planting tender crops after May 14 leaves a 30% risk of a frost on them, after May 17 20%, and after May 22 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 September 29 in half of years, as early as September 17 one year in ten, and holds off past October 12 one year in ten. A hard freeze of 28°F follows 7 days later, around October 6; in spring the one-in-ten date for 28°F is May 12, 10 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 161 days one year in ten and falls short of 125 one year in ten. On average 180 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 18, and return around September 21. Severe cold of 16°F or below comes every winter, usually between November 4 and April 3.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 5 | May 10 | May 13 | May 16 | May 18 | May 21 | May 24 | May 27 | May 30 |
| 32°F | Apr 26 | Apr 30 | May 3 | May 6 | May 8 | May 11 | May 14 | May 17 | May 22 |
| 28°F | Apr 16 | Apr 21 | Apr 24 | Apr 27 | Apr 30 | May 2 | May 4 | May 7 | May 12 |
| 24°F | Apr 7 | Apr 11 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 27 | Apr 30 | May 4 |
| 20°F | Mar 29 | Apr 3 | Apr 6 | Apr 9 | Apr 12 | Apr 16 | Apr 19 | Apr 23 | Apr 28 |
| 16°F | Mar 18 | Mar 23 | Mar 29 | Apr 1 | Apr 3 | Apr 6 | Apr 9 | Apr 13 | Apr 19 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 8 | Sep 12 | Sep 16 | Sep 19 | Sep 21 | Sep 23 | Sep 25 | Sep 28 | Oct 2 |
| 32°F | Sep 17 | Sep 21 | Sep 24 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 6 | Oct 12 |
| 28°F | Sep 24 | Sep 28 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 13 | Oct 16 | Oct 20 |
| 24°F | Oct 1 | Oct 6 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 25 | Oct 29 |
| 20°F | Oct 10 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 3 | Nov 8 |
| 16°F | Oct 22 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 13 | Nov 19 |
Freeze probabilities 1991–2020 at Ipswich, 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 57451 →Compare Ipswich with another place →
Weather by month in Ipswich
July is the warmest month at Ipswich, SD, averaging 84°F by day and 59°F at night; January is the coldest at 24°F and 3°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 78% of years.
Warmth for growing adds up to 2,446 growing degree days a year (base 50°F), fewer than at 76% of the 49 South Dakota stations. 32% of them (785) have built up by the end of June, and July adds the most, 668. Precipitation totals 20.2 inches a year, most in June (3.5") and least in January (0.4"); May to September bring 69% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 24 | 3 | 0.4 | 100% | 31 | 0 |
| Feb | 28 | 7 | 0.5 | 100% | 28 | 0 |
| Mar | 41 | 19 | 0.9 | 100% | 28 | 5 |
| Apr | 57 | 31 | 1.8 | 100% | 17 | 45 |
| May | 69 | 44 | 3.0 | 78% | 3 | 236 |
| Jun | 79 | 55 | 3.5 | 0% | 0 | 498 |
| Jul | 84 | 59 | 3.1 | 0% | 0 | 668 |
| Aug | 82 | 57 | 2.4 | 0% | 0 | 595 |
| Sep | 74 | 47 | 1.9 | 57% | 1 | 321 |
| Oct | 58 | 34 | 1.7 | 100% | 14 | 73 |
| Nov | 42 | 20 | 0.5 | 100% | 27 | 3 |
| Dec | 28 | 9 | 0.5 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Ipswich, SD (1,547 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, Aberdeen 3 E, SD, 29 miles east of Ipswich and 246 feet lower, has the same 50% last-frost date, the same first-frost date, a season 1 day longer.
When it snows in Ipswich, South Dakota
The first measurable snow (0.1 inch or more) in Ipswich usually arrives around November 9, and the last of the season around April 6. Those are the middle dates across the winters of 1991–2020 at Ipswich, SD, 1.1 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 32 days after the last snow.
Planting calendar for 57451
| When | What to do |
|---|---|
| February 27 – March 13 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 13 – March 27 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 10 – April 24 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 8 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 7 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 15 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 29 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 57451 is 1 mile from Ipswich, SD, which stands at 1,547 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 57451 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.