USDA Hardiness Zone 4a
Frost Dates for 58012 — Casselton, North Dakota
NOAA 1991–2020 normals from Casselton Agronomy Farm, ND (935 ft), 3 miles southwest.
Updated
In Casselton, the last spring frost (32°F) is around May 9 in half of years and has passed by May 21 in nine years out of ten. The first fall frost comes around October 1, as early as September 17 one year in ten, leaving a typical freeze-free season of 143 days (NOAA, Casselton Agronomy Farm, ND).
- Last spring frost
- May 9
- First fall frost
- October 1
- Growing season
- 143 days
- Hardiness zone
- 4a
50% probability
50% probability
freeze-free, 50%
-30 to -25°F (-34.4 to -31.7°C) coldest night
- First snow
- November 12
- Last snow
- March 30
- Winters with snow
- 100%
- Snow per year
- 36.7"
median, 1991–2020
median, 1991–2020
23 of 23 observed
NOAA normal
Frost risk by date in Casselton
Half of springs at Casselton Agronomy Farm, ND see their last 32°F night by May 9; only one in ten is past it by April 25, and one in ten still has one after May 21. Planting tender crops after May 14 leaves a 30% risk of a frost on them, after May 17 20%, and after May 21 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 79% of the 33 North Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 1 in half of years, as early as September 17 one year in ten, and holds off past October 15 one year in ten. A hard freeze of 28°F follows 9 days later, around October 10; in spring the one-in-ten date for 28°F is May 13, 8 days before the 32°F one. The freeze-free season lasts 143 days in a typical year, longer than at 73% of the 33 North Dakota stations; it reaches 163 days one year in ten and falls short of 126 one year in ten. On average 182 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 9 days longer, to about May 18, and return around September 22. Severe cold of 16°F or below comes every winter, usually between November 7 and April 3.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 4 | May 9 | May 12 | May 15 | May 18 | May 20 | May 22 | May 25 | May 29 |
| 32°F | Apr 25 | Apr 30 | May 3 | May 5 | May 9 | May 11 | May 14 | May 17 | May 21 |
| 28°F | Apr 12 | Apr 18 | Apr 22 | Apr 26 | Apr 29 | May 1 | May 4 | May 9 | May 13 |
| 24°F | Apr 5 | Apr 8 | Apr 11 | Apr 14 | Apr 18 | Apr 21 | Apr 25 | Apr 28 | May 3 |
| 20°F | Mar 27 | Apr 1 | Apr 4 | Apr 6 | Apr 8 | Apr 11 | Apr 13 | Apr 18 | Apr 24 |
| 16°F | Mar 17 | Mar 24 | Mar 29 | Apr 1 | Apr 3 | Apr 5 | Apr 7 | Apr 11 | Apr 16 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 10 | Sep 14 | Sep 17 | Sep 19 | Sep 22 | Sep 24 | Sep 26 | Sep 29 | Oct 3 |
| 32°F | Sep 17 | Sep 22 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 6 | Oct 9 | Oct 15 |
| 28°F | Sep 26 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 14 | Oct 17 | Oct 21 | Oct 24 |
| 24°F | Oct 4 | Oct 10 | Oct 13 | Oct 18 | Oct 21 | Oct 25 | Oct 28 | Oct 31 | Nov 3 |
| 20°F | Oct 14 | Oct 22 | Oct 25 | Oct 28 | Oct 31 | Nov 2 | Nov 5 | Nov 8 | Nov 13 |
| 16°F | Oct 26 | Oct 31 | Nov 2 | Nov 4 | Nov 7 | Nov 10 | Nov 13 | Nov 16 | Nov 22 |
Freeze probabilities 1991–2020 at Casselton Agronomy Farm, ND, 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 58012 →Compare Casselton with another place →
Weather by month in Casselton
July is the warmest month at Casselton Agronomy Farm, ND, averaging 81°F by day and 59°F at night; January is the coldest at 17°F and -1°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 77% of years.
Warmth for growing adds up to 2,246 growing degree days a year (base 50°F), more than at 67% of the 33 North Dakota stations. 33% of them (735) have built up by the end of June, and July adds the most, 611. Precipitation totals 24.2 inches a year, most in June (4.4") and least in January (0.5"); May to September bring 69% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 17 | -1 | 0.5 | 100% | 31 | 0 |
| Feb | 22 | 2 | 0.6 | 100% | 28 | 0 |
| Mar | 35 | 17 | 1.1 | 100% | 28 | 1 |
| Apr | 53 | 31 | 1.5 | 100% | 18 | 34 |
| May | 68 | 43 | 3.2 | 77% | 3 | 220 |
| Jun | 77 | 55 | 4.4 | 0% | 0 | 479 |
| Jul | 81 | 59 | 3.7 | 0% | 0 | 611 |
| Aug | 80 | 56 | 2.6 | 0% | 0 | 553 |
| Sep | 71 | 46 | 2.8 | 48% | 2 | 287 |
| Oct | 56 | 34 | 2.3 | 100% | 14 | 59 |
| Nov | 38 | 20 | 0.8 | 100% | 27 | 1 |
| Dec | 23 | 7 | 0.7 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Casselton Agronomy Farm, ND (935 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, Fargo Hector International Airport, ND, 18 miles east of Casselton, has a last frost 1 day later (May 10), a first frost 1 day earlier (September 30).
When it snows in Casselton, North Dakota
The first measurable snow (0.1 inch or more) in Casselton usually arrives around November 12, and the last of the season around March 30. Those are the middle dates across the winters of 1991–2020 at Casselton Agronomy Farm, ND, 3.2 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 40 days after the last snow.
Planting calendar for 58012
| When | What to do |
|---|---|
| February 28 – March 14 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 14 – March 28 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 11 – April 25 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 9 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 9 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 17 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 1 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 58012 is 3 miles from Casselton Agronomy Farm, ND, which stands at 935 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 58012 in zone 4a, the band where the coldest night of the year averaged -30 to -25°F (-34.4 to -31.7°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across North 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.