USDA Hardiness Zone 4a
Frost Dates for 58237 — Grafton, North Dakota
NOAA 1991–2020 normals from Grafton, ND (827 ft), under a mile west.
Updated
In Grafton, the last spring frost (32°F) is around May 4 in half of years and has passed by May 18 in nine years out of ten. The first fall frost comes around October 7, as early as September 25 one year in ten, leaving a typical freeze-free season of 156 days (NOAA, Grafton, ND).
- Last spring frost
- May 4
- First fall frost
- October 7
- Growing season
- 156 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 7
- Last snow
- April 12
- Winters with snow
- 100%
- Snow per year
- 43.6"
median, 1991–2020
median, 1991–2020
29 of 29 observed
NOAA normal
Frost risk by date in Grafton
Half of springs at Grafton, ND see their last 32°F night by May 4; only one in ten is past it by April 19, and one in ten still has one after May 18. Planting tender crops after May 9 leaves a 30% risk of a frost on them, after May 13 20%, and after May 18 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 82% of the 33 North Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 7 in half of years, as early as September 25 one year in ten, and holds off past October 21 one year in ten. A hard freeze of 28°F follows 10 days later, around October 17; in spring the one-in-ten date for 28°F is May 9, 9 days before the 32°F one. The freeze-free season lasts 156 days in a typical year, longer than at 97% of the 33 North Dakota stations; it reaches 176 days one year in ten and falls short of 137 one year in ten. On average 169 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 13, and return around September 28. Severe cold of 16°F or below comes every winter, usually between November 9 and April 2.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 30 | May 4 | May 7 | May 10 | May 13 | May 15 | May 18 | May 22 | May 26 |
| 32°F | Apr 19 | Apr 24 | Apr 28 | May 1 | May 4 | May 6 | May 9 | May 13 | May 18 |
| 28°F | Apr 9 | Apr 14 | Apr 18 | Apr 21 | Apr 24 | Apr 27 | Apr 30 | May 4 | May 9 |
| 24°F | Apr 1 | Apr 5 | Apr 9 | Apr 12 | Apr 15 | Apr 19 | Apr 22 | Apr 25 | Apr 30 |
| 20°F | Mar 23 | Mar 30 | Apr 2 | Apr 5 | Apr 8 | Apr 10 | Apr 14 | Apr 18 | Apr 23 |
| 16°F | Mar 17 | Mar 22 | Mar 26 | Mar 31 | Apr 2 | Apr 4 | Apr 7 | Apr 10 | Apr 16 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Sep 28 | Oct 1 | Oct 3 | Oct 6 | Oct 10 |
| 32°F | Sep 25 | Sep 29 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 12 | Oct 17 | Oct 21 |
| 28°F | Oct 3 | Oct 7 | Oct 11 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 30 |
| 24°F | Oct 12 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 8 |
| 20°F | Oct 20 | Oct 26 | Oct 29 | Nov 1 | Nov 3 | Nov 5 | Nov 8 | Nov 11 | Nov 16 |
| 16°F | Oct 28 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 18 | Nov 23 |
Freeze probabilities 1991–2020 at Grafton, 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 58237 →Compare Grafton with another place →
Weather by month in Grafton
July is the warmest month at Grafton, ND, averaging 81°F by day and 61°F at night; January is the coldest at 16°F and 0°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 61% of years.
Warmth for growing adds up to 2,527 growing degree days a year (base 50°F), the most of the 33 North Dakota stations. 34% of them (862) have built up by the end of June, and July adds the most, 659.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 16 | 0 | 100% | 31 | 0 |
| Feb | 21 | 4 | 100% | 27 | 0 |
| Mar | 34 | 19 | 100% | 26 | 1 |
| Apr | 53 | 33 | 100% | 14 | 48 |
| May | 68 | 46 | 61% | 2 | 275 |
| Jun | 79 | 57 | 0% | 0 | 539 |
| Jul | 81 | 61 | 0% | 0 | 659 |
| Aug | 80 | 59 | 0% | 0 | 607 |
| Sep | 71 | 50 | 24% | 1 | 332 |
| Oct | 54 | 36 | 98% | 11 | 64 |
| Nov | 36 | 22 | 100% | 27 | 3 |
| Dec | 21 | 7 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Grafton, ND (827 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, Warren Wsd, MN, 33 miles southeast of Grafton, has a last frost 1 day later (May 5), a first frost 5 days earlier (October 2), a season 9 days shorter.
When it snows in Grafton, North Dakota
The first measurable snow (0.1 inch or more) in Grafton usually arrives around November 7, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Argyle, MN, 27.5 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 22 days after the last snow.
Planting calendar for 58237
| When | What to do |
|---|---|
| February 23 – March 9 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 9 – March 23 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 6 – April 20 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 4 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 15 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 23 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 7 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 58237 is under a mile from Grafton, ND, which stands at 827 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 58237 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.